Build improvements

[Thelta]

Setting up Orbit on ArchLinux wasn't easy, but I made some tweaks to make it work better. I also wanted to journal my fixes.

1. Added boost version header to third_party/Outcome/outcome.hpp. Before that, because header was not included, BOOST_VERSION was evaluated to 0 and was using wrong definitions which caused build errors. Probably cause of Doesn't build with Boost outcome #4822.

2. For my compiler (gcc 13.2), libprocinfo was giving ignored attributes warning, which caused error because of Wall. Passed Wno-error for this warning to libprocinfo target.

3. In ArchLinux, LLVM libraries is distributed via a singular shared library libLLVM.so. Search this library in found LLVM's library path, if found use it, if not use the static libraries.

4. Currently Orbit uses grpc, protobuf and abseil, however only abseil is forced to be built if conan is not used. This causes errors because in ArchLinux distribution of protobuf uses much newer abseil than Orbit's abseil and this causes errors. Currently finding if abseil is built with C++17 or not is not possible, so warn the users about it and how to circumvent it.

With these patches only one build error remains, current ArchLinux distribution of protobuf is not compatible this repo's libprotobuf-mutator. However this would required adding patches to a third party library, which I am wary. So I decided to add this patch to not here but my own Orbit repo.

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[pierricgimmig]

@Thelta, thanks a lot for the PR. This looks good to me, but perhaps @beckerhe can also have a look. I kicked off the CI, let's see if everything still builds fine on Ubuntu and Windows.

[beckerhe]

Thank you for the fixes and sorry for the delay. According to the CI there is an issue with the LLVM change

[beckerhe]

Looking at the CI results now. I don't think this works. What exactly would you like to achieve here?

[Thelta]

First it tries to find libLLVM.so (this shared library includes everything and some distributions only includes this library). If not then tries to use the static libraries (LLVMDebugInfoCodeView, LLVMDebugInfoDWARF etc).

However I made two mistakes.

1. I assumed distributions either released only shared library (libLLVM.so) or static libraries. However in ubuntu's case (and probably others) they also release the shared library. This resulted LLVM_LIBS only using libLLVM.so

2. Because of above, LLVMHeaders, which is not a static library but a interface target which includes LLVM headers, are not included. This causes the build errors.

9c3160 should fix both issues. With this patch, it first searches the necessary llvm static libraries, if one is not found, then uses the shared library. I also readded LLVMHeaders to target_link_libraries directly.

[pierricgimmig]

@Thelta, could you rebase on latest main, the Windows build is fixed now with #4851. Thanks!

[pierricgimmig]

lgtm

[pierricgimmig]

Looks like the Windows build is failing:

CMake Warning at cmake/FindLLVM.cmake:13 (find_package):
  Could not find a configuration file for package "LLVM" that is compatible
  with requested version "14".

[Thelta]

Looks like the Windows build is failing:

CMake Warning at cmake/FindLLVM.cmake:13 (find_package):
  Could not find a configuration file for package "LLVM" that is compatible
  with requested version "14".

Yeah it seems unlike vcpkg, conan directly loads dependencies as targets. New rebase should fix it.

[pierricgimmig]

Thanks for the change, @Thelta !