Cmake may not detect ar path when building DeepState AFL

[disconnect3d]

Tl;dr: I stumbled upon cmake not detecting the ar path while it is clearly in my Ubuntu 18.04 installation.

The issue is that some generated file contains the CMAKE_AR-NOTFOUND instead of ar path. I resolved it locally by specyfing -D CMAKE_AR=/usr/bin/ar as suggested here.

root@b2e78972f3fa:~/deepstate/build_afl# CXX="$AFL_HOME/afl-clang++" CC="$AFL_HOME/afl-clang" cmake -DDEEPSTATE_AFL=ON ../
-- The C compiler identification is Clang 6.0.0
-- The CXX compiler identification is Clang 6.0.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /root/AFL/afl-clang - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /root/AFL/afl-clang++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: /root/deepstate/build_afl

root@b2e78972f3fa:~/deepstate/build_afl# make
Scanning dependencies of target deepstate_AFL
[  1%] Building C object CMakeFiles/deepstate_AFL.dir/src/lib/DeepState.c.o
afl-cc 2.57b by <lcamtuf@google.com>
afl-as 2.57b by <lcamtuf@google.com>
[+] Instrumented 1205 locations (64-bit, non-hardened mode, ratio 100%).
[  2%] Building C object CMakeFiles/deepstate_AFL.dir/src/lib/Log.c.o
afl-cc 2.57b by <lcamtuf@google.com>
afl-as 2.57b by <lcamtuf@google.com>
[+] Instrumented 43 locations (64-bit, non-hardened mode, ratio 100%).
[  3%] Building C object CMakeFiles/deepstate_AFL.dir/src/lib/Option.c.o
afl-cc 2.57b by <lcamtuf@google.com>
afl-as 2.57b by <lcamtuf@google.com>
[+] Instrumented 285 locations (64-bit, non-hardened mode, ratio 100%).
[  5%] Building C object CMakeFiles/deepstate_AFL.dir/src/lib/Stream.c.o
afl-cc 2.57b by <lcamtuf@google.com>
afl-as 2.57b by <lcamtuf@google.com>
[+] Instrumented 280 locations (64-bit, non-hardened mode, ratio 100%).
[  6%] Linking C static library libdeepstate_AFL.a
Error running link command: No such file or directory
CMakeFiles/deepstate_AFL.dir/build.make:147: recipe for target 'libdeepstate_AFL.a' failed
make[2]: *** [libdeepstate_AFL.a] Error 2
CMakeFiles/Makefile2:178: recipe for target 'CMakeFiles/deepstate_AFL.dir/all' failed
make[1]: *** [CMakeFiles/deepstate_AFL.dir/all] Error 2
Makefile:136: recipe for target 'all' failed
make: *** [all] Error 2

root@b2e78972f3fa:~/deepstate/build_afl# cat CMakeFiles//deepstate_AFL.dir/link.txt
CMAKE_AR-NOTFOUND qc libdeepstate_AFL.a CMakeFiles/deepstate_AFL.dir/src/lib/DeepState.c.o CMakeFiles/deepstate_AFL.dir/src/lib/Log.c.o CMakeFiles/deepstate_AFL.dir/src/lib/Option.c.o CMakeFiles/deepstate_AFL.dir/src/lib/Stream.c.o

root@b2e78972f3fa:~/deepstate/build_afl# apt install ar
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package ar
root@b2e78972f3fa:~/deepstate/build_afl# ar
Usage: ar [emulation options] [-]{dmpqrstx}[abcDfilMNoPsSTuvV] [--plugin <name>] [member-name] [count] archive-file file...
       ar -M [<mri-script]