Added check for /usr/lib64 for fix issue in Fedora 33

[andrewxcav]

Effects:

• If your initial call to cmake worked before it should still work
• If you had the same issue I had with the existence of /lib64 this fixes it
• CMakeLists.txt is a bit more cluttered though

I think this will lower a significant barrier to folks who are going to install the llvm-devel package but not necessarily build llvm-project from source.

[banach-space]

Hi @andrewxcav ,

Many thanks for looking into this and submitting a fix! I didn't realise that there were issues on Fedora - good catch! I've just created #32 and will try to set something up to better defend against things like this in the future. Volunteers are always very welcome ;-)

Note that your change will only silence the CMake error. I think that you also need to update:

• https://github.com/banach-space/llvm-tutor/blob/main/CMakeLists.txt#L29
• https://github.com/banach-space/llvm-tutor/blob/main/HelloWorld/CMakeLists.txt#L12

I suspect that find_package(LLVM REQUIRED CONFIG) works for you anyway as your LLVM installation is in some "standard" location (i.e. "auto-magically" included in CMake's search path).

Last, but not least - would you mind adding a short note in CMake scripts explaining the reasoning behind duplicating set(LT_LLVM_CMAKE_FILE ...)? The commit message explains it really well, but it's a rather tricky and IMHO worth documenting in as many places as possible.

Thanks again for submitting this!

-Andrzej

PS BTW, I am about to update llvm-tutor to LLVM 12, which should fix the CI failure.

[banach-space]

@andrewxcav , I've just updated llvm-tutor to LLVM 12. Could you re-base, please? I hope that this goes smoothly for you! Let me know if you hit any problems.

[banach-space]

This thread has gone a bit stale :)

This is a much needed change and I will merge it as is! With the new Fedora docker set-up, I will be able to test and fine-tune it (if required).

Thank you @andrewxcav !