[bug] "None" is not a known value of feature <cxxstd>

[rdong8]

Describe the bug

OS: Fedora 41
Compiler: Clang 19.1.0
Conan version: 2.9.2
Conan profile:

[buildenv]
CC=clang
CXX=clang++

[conf]
tools.cmake.cmaketoolchain:generator=Ninja Multi-Config

[platform_tool_requires]
cmake/3.31.0

[settings]
arch=x86_64
build_type=Release
compiler=clang
compiler.cppstd=26
compiler.libcxx=libc++
compiler.version=19
os=Linux

I get this error when trying to build boost 1.86.0:

BUILD_DIR=build/ \
        conan \
                install . \
                -b missing \
                -s build_type=Release \
                -s "&:build_type=Debug"

======== Input profiles ========
Profile host:
[settings]
arch=x86_64
build_type=Release
compiler=clang
compiler.cppstd=26
compiler.libcxx=libc++
compiler.version=19
os=Linux
&:build_type=Debug
[platform_tool_requires]
cmake/3.31.0
[conf]
tools.cmake.cmaketoolchain:generator=Ninja Multi-Config
[buildenv]
CC=clang
CXX=clang++

Profile build:
[settings]
arch=x86_64
build_type=Release
compiler=clang
compiler.cppstd=26
compiler.libcxx=libc++
compiler.version=19
os=Linux
[platform_tool_requires]
cmake/3.31.0
[conf]
tools.cmake.cmaketoolchain:generator=Ninja Multi-Config
[buildenv]
CC=clang
CXX=clang++


======== Computing dependency graph ========
Graph root
    conanfile.py: /home/rd8/tmp/spdlog/conanfile.py
Requirements
    boost/1.86.0#46c984e8737c8b910597294db3838f3b - Cache
    bzip2/1.0.8#d00dac990f08d991998d624be81a9526 - Cache
    libbacktrace/cci.20210118#a7691bfccd8caaf66309df196790a5a1 - Cache
    zlib/1.3.1#f52e03ae3d251dec704634230cd806a2 - Cache
Build requirements
    b2/5.2.1#91bc73931a0acb655947a81569ed8b80 - Cache
Resolved version ranges
    b2/[>=5.2 <6]: b2/5.2.1
    zlib/[>=1.2.11 <2]: zlib/1.3.1

======== Computing necessary packages ========
boost/1.86.0: Main binary package 'c123612e482b0a8ecc61a6ddb0a62d25e7578366' missing
boost/1.86.0: Checking 5 compatible configurations
boost/1.86.0: Compatible configurations not found in cache, checking servers
boost/1.86.0: 'af3e0258503efbefd0af55b4f2db656adc861436': compiler.cppstd=20
boost/1.86.0: '3427da6b3ac26939436d8224d9e5ec48f192a412': compiler.cppstd=gnu20
boost/1.86.0: 'cbf236643def2491b4668a4a48b7a8131c6d5623': compiler.cppstd=23
boost/1.86.0: 'c9e387a2d958cc83509b4521866344929375614a': compiler.cppstd=gnu23
boost/1.86.0: '728d5f8f5ab862ab57258b1bfca76baba484a027': compiler.cppstd=gnu26
Requirements
    boost/1.86.0#46c984e8737c8b910597294db3838f3b:c123612e482b0a8ecc61a6ddb0a62d25e7578366 - Build
    bzip2/1.0.8#d00dac990f08d991998d624be81a9526:ab19b9bfc1b47ea17e1a675221a2f0b1e27ebba5#828dec56fc764c5a7b453a74909975da - Cache
    libbacktrace/cci.20210118#a7691bfccd8caaf66309df196790a5a1:035983102d94f5d9d7256017a5fd89651d1294c3#23a7486ad0b011d9c32d47614535c965 - Cache
    zlib/1.3.1#f52e03ae3d251dec704634230cd806a2:035983102d94f5d9d7256017a5fd89651d1294c3#703bf4613eab5db64f0ed0471910cae8 - Cache
Build requirements
    b2/5.2.1#91bc73931a0acb655947a81569ed8b80:63fead0844576fc02943e16909f08fcdddd6f44b#f9c46d924270b1920fa5398114be2576 - Cache

======== Installing packages ========
b2/5.2.1: Already installed! (1 of 5)
bzip2/1.0.8: Already installed! (2 of 5)
libbacktrace/cci.20210118: Already installed! (3 of 5)
zlib/1.3.1: Already installed! (4 of 5)

-------- Installing package boost/1.86.0 (5 of 5) --------
boost/1.86.0: Building from source
boost/1.86.0: Package boost/1.86.0:c123612e482b0a8ecc61a6ddb0a62d25e7578366
boost/1.86.0: Building your package in /home/rd8/.conan2/p/b/boostbfbe5e40d48ba/b
boost/1.86.0: Calling generate()
boost/1.86.0: Generators folder: /home/rd8/.conan2/p/b/boostbfbe5e40d48ba/b/build-release/conan
boost/1.86.0: Generating aggregated env files
boost/1.86.0: Generated aggregated env files: ['conanbuild.sh', 'conanrun.sh']
boost/1.86.0: Calling build()
boost/1.86.0: WARN: replace_in_file didn't find pattern '/* thread_local */' in '/home/rd8/.conan2/p/boost64c835a1b022d/s/src/boost/stacktrace/detail/libbacktrace_impls.hpp' file.
boost/1.86.0: WARN: replace_in_file didn't find pattern '/* static __thread */' in '/home/rd8/.conan2/p/boost64c835a1b022d/s/src/boost/stacktrace/detail/libbacktrace_impls.hpp' file.
boost/1.86.0: WARN: replace_in_file didn't find pattern 'local generic-os = [ set.difference $(all-os) : aix darwin vxworks solaris osf hpux ] ;' in '/home/rd8/.conan2/p/boost64c835a1b022d/s/src/tools/build/src/tools/gcc.jam' file.
boost/1.86.0: WARN: replace_in_file didn't find pattern 'local no-threading = android beos haiku sgi darwin vxworks ;' in '/home/rd8/.conan2/p/boost64c835a1b022d/s/src/tools/build/src/tools/gcc.jam' file.
boost/1.86.0: WARN: replace_in_file didn't find pattern '    <conditional>@numa' in '/home/rd8/.conan2/p/boost64c835a1b022d/s/src/libs/fiber/build/Jamfile.v2' file.
boost/1.86.0: WARN: Patching user-config.jam
boost/1.86.0: WARN:
using zlib : 1.3.1 : <include>"/home/rd8/.conan2/p/b/zlibcaf5fbf98ae52/p/include" <search>"/home/rd8/.conan2/p/b/zlibcaf5fbf98ae52/p/lib" <name>z ;
using bzip2 : 1.0.8 : <include>"/home/rd8/.conan2/p/b/bzip22f874f58d689a/p/include" <search>"/home/rd8/.conan2/p/b/bzip22f874f58d689a/p/lib" <name>bz2 ;
using "clang" :  :  "clang++" :
<compileflags>"-I/home/rd8/.conan2/p/b/libbad2cd77a9b6ae3/p/include" <linkflags>"-L/home/rd8/.conan2/p/b/libbad2cd77a9b6ae3/p/lib"  ;
boost/1.86.0: WARN: b2 -q numa=on target-os=linux architecture=x86 address-model=64 binary-format=elf abi=sysv --layout=system --user-config=/home/rd8/.conan2/p/boost64c835a1b022d/s/src/tools/build/user-config.jam -sNO_ZLIB=0 -sNO_BZIP2=0 -sNO_LZMA=1 -sNO_ZSTD=1 boost.locale.icu=off --disable-icu boost.locale.iconv=on boost.locale.iconv.lib=libc threading=multi visibility=hidden link=static variant=release --with-atomic --with-charconv --with-chrono --with-cobalt --with-container --with-context --with-contract --with-coroutine --with-date_time --with-exception --with-fiber --with-filesystem --with-graph --with-iostreams --with-json --with-locale --with-log --with-math --with-nowide --with-process --with-program_options --with-random --with-regex --with-serialization --with-stacktrace --with-system --with-test --with-thread --with-timer --with-type_erasure --with-url --with-wave toolset=clang cxxstd=None pch=on -sLIBBACKTRACE_PATH=/home/rd8/.conan2/p/b/libbad2cd77a9b6ae3/p linkflags="-stdlib=libc++" cxxflags="-fPIC -stdlib=libc++ -DBOOST_STACKTRACE_ADDR2LINE_LOCATION=/usr/bin/addr2line" install --prefix=/home/rd8/.conan2/p/b/boostbfbe5e40d48ba/p -j16 --abbreviate-paths -d0 --debug-configuration --build-dir="/home/rd8/.conan2/p/b/boostbfbe5e40d48ba/b/build-release"
boost/1.86.0: RUN: b2 -q numa=on target-os=linux architecture=x86 address-model=64 binary-format=elf abi=sysv --layout=system --user-config=/home/rd8/.conan2/p/boost64c835a1b022d/s/src/tools/build/user-config.jam -sNO_ZLIB=0 -sNO_BZIP2=0 -sNO_LZMA=1 -sNO_ZSTD=1 boost.locale.icu=off --disable-icu boost.locale.iconv=on boost.locale.iconv.lib=libc threading=multi visibility=hidden link=static variant=release --with-atomic --with-charconv --with-chrono --with-cobalt --with-container --with-context --with-contract --with-coroutine --with-date_time --with-exception --with-fiber --with-filesystem --with-graph --with-iostreams --with-json --with-locale --with-log --with-math --with-nowide --with-process --with-program_options --with-random --with-regex --with-serialization --with-stacktrace --with-system --with-test --with-thread --with-timer --with-type_erasure --with-url --with-wave toolset=clang cxxstd=None pch=on -sLIBBACKTRACE_PATH=/home/rd8/.conan2/p/b/libbad2cd77a9b6ae3/p linkflags="-stdlib=libc++" cxxflags="-fPIC -stdlib=libc++ -DBOOST_STACKTRACE_ADDR2LINE_LOCATION=/usr/bin/addr2line" install --prefix=/home/rd8/.conan2/p/b/boostbfbe5e40d48ba/p -j16 --abbreviate-paths -d0 --debug-configuration --build-dir="/home/rd8/.conan2/p/b/boostbfbe5e40d48ba/b/build-release"
notice: found boost-build.jam at /home/rd8/.conan2/p/boost64c835a1b022d/s/src/boost-build.jam
notice: loading B2 from /home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/build-system.jam
notice: Searching '/etc' '/home/rd8' '/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/util' '/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/tools' '/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/options' '/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/contrib' '/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/build' '/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2' for site-config configuration file 'site-config.jam'.
notice: Configuration file 'site-config.jam' not found in '/etc' '/home/rd8' '/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/util' '/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/tools' '/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/options' '/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/contrib' '/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/build' '/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2'.
notice: Loading explicitly specified user configuration file:
    /home/rd8/.conan2/p/boost64c835a1b022d/s/src/tools/build/user-config.jam
notice: Searching '/home/rd8/.conan2/p/boost64c835a1b022d/s/src/tools/build' for user-config configuration file 'user-config.jam'.
notice: Loading user-config configuration file 'user-config.jam' from '/home/rd8/.conan2/p/boost64c835a1b022d/s/src/tools/build'.
notice: [zlib] Using pre-installed library
notice: [zlib] Condition
notice: [bzip2] Using pre-installed library
notice: [bzip2] Condition
notice: will use 'clang++' for clang-linux, condition <toolset>clang-linux-19
warning: toolset clang-linux initialization: can not find tool windres
warning: initialized from /home/rd8/.conan2/p/boost64c835a1b022d/s/src/tools/build/user-config.jam:5
notice: using rc compiler :: <toolset>clang-linux-19 :: as
notice: [openssl] Using pre-installed library
notice: [openssl] Condition
notice: using boost library auto_config <layout>system
notice: [zlib] zlib is already configured
notice: [bzip2] bzip is already configured
notice: iostreams: not using lzma compression
notice: iostreams: not using zstd compression
notice: [python-cfg] Configuring python...
notice: [python-cfg] Checking interpreter command "python"...
notice: [python-cfg] running command 'python -c "from sys import *; print('version=%d.%d\nplatform=%s\nprefix=%s\nexec_prefix=%s\nexecutable=%s' % (version_info[0],version_info[1],platform,prefix,exec_prefix,executable))" 2>&1'
notice: [python-cfg] ...requested configuration matched!
notice: [python-cfg] Details of this Python configuration:
notice: [python-cfg]   interpreter command: "python"
notice: [python-cfg]   include path: "/home/rd8/tmp/spdlog/.venv/include/python3.13"
notice: [python-cfg]   library path: "/home/rd8/tmp/spdlog/.venv/lib/python3.13/config" "/home/rd8/tmp/spdlog/.venv/lib"
notice: [python-cfg] Checking for NumPy...
notice: [python-cfg] running command 'python -c "import sys; sys.stderr = sys.stdout; import numpy; print(numpy.get_include())"'
notice: [python-cfg] NumPy disabled. Reason:
notice: [python-cfg]   python -c "import sys; sys.stderr = sys.stdout; import numpy; print(numpy.get_include())" aborted with
notice: [python-cfg]   Traceback (most recent call last):
  File "<string>", line 1, in <module>
    import sys; sys.stderr = sys.stdout; import numpy; print(numpy.get_include())
                                         ^^^^^^^^^^^^
ModuleNotFoundError: No module named 'numpy'
/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/build/feature.jam:491: in feature.validate-value-string from module feature
error: "None" is not a known value of feature <cxxstd>
error: legal values: "98" "03" "0x" "11" "1y" "14" "1z" "17" "2a" "20" "2b" "23" "2c" "26" "latest"
/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/build/property.jam:346: in validate1 from module property
/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/build/property.jam:372: in property.validate from module property
/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/build/build-request.jam:286: in convert-command-line-element from module build-request
/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/build/build-request.jam:222: in build-request.convert-command-line-elements from module build-request
/home/rd8/.conan2/p/b20717b8c0763fa/p/bin/.b2/build-system.jam:774: in module scope from module build-system

boost/1.86.0: ERROR:
Package 'c123612e482b0a8ecc61a6ddb0a62d25e7578366' build failed
boost/1.86.0: WARN: Build folder /home/rd8/.conan2/p/b/boostbfbe5e40d48ba/b/build-release
ERROR: boost/1.86.0: Error in build() method, line 1163
        self.run(full_command)
        ConanException: Error 1 while executing

How to reproduce it

boost.zip

Run:

make conan