[clang] [clang] Add `intrin0.h` header to mimic `intrin0.h` used by MSVC STL for clang-cl (PR #75711)

[Nico Weber via cfe-commits]

nico wrote:

Is `intrin0.h` a header that ships with MSVC's compiler, or with MS's STL? If the latter, shouldn't everything just work already?

https://github.com/llvm/llvm-project/pull/75711