[RFC] Clang 17.0.6 would be minimum version to build LLVM in C++20

[MaskRay]

@jyknight

For reasonable C++20 compiler support, I’ve been making a recommendation of the following minimum compiler versions:

• Clang 17
• GCC 12
• MSVC 17.2

…and don’t use coroutines or modules yet, both of which are not yet fully-baked.

So, this proposal would really only raise the realistic minimum for building LLVM in C++20 mode from “17.0.0” to “17.0.6”.

I support this proposal, when CMAKE_CXX_STANDARD=20, we impose higher compiler version requirement.

Has anyone tested GCC 12 or MSVC 17.2?