[clang] [clang] Improve diagnostic if intrin.h used in incompatible environments (PR #234114)

[via cfe-commits]

gallopruss-sie wrote:

@rnk @mstorsjo , please could you review?

I believe that this is correct behaviour, and should continue to work fine on Windows and MinGW environments, but there may be a case that I'm not aware of.

https://github.com/llvm/llvm-project/pull/234114