doesn't work on arch linux

[garobrik]

arch linux installation simply provides a clang binary and a single shared library, which doesn't work with the current CMake file. we need to modify the cmake file to also support arch linux.

also, the compile_commands generated on arch linux have a wonky system include path, which precludes any code intelligence from standard library functions.

[aidaeology]

@gbrik What is the status of this issue, was this resolved with the 3.20 milestone or does it still need work? If it's resolved and longer a problem then please mark as closed and link the relevant PR. Otherwise please provide a status update here on what the remaining work is to get it resolved.