[clang] [X86][Clang] allow CRC32 intrinsics to be used in constexp (PR #173908)

[Simon Pilgrim via cfe-commits]

https://github.com/RKSimon commented:

For this kind of thing I like to fuzz the values as much as possible: 
https://simd.godbolt.org/z/7TsdxYfdE - generates a few test cases for you

but ideally you should be able to dump a lot of random values and compare the runtime and constexpr results to ensure they all match.

https://github.com/llvm/llvm-project/pull/173908