[compiler-rt] [compiler-rt][MSVC] Conditionally remove emupac.cpp for msvc (PR #149823)

[Nico Weber via llvm-commits]

nico wrote:

"MSVC" is true both for msvc and clang-cl. Do you want to exclude this for clang-cl too? (I.e. is this about a cl.exe limitation, or a PE/COFF limitation?)

https://github.com/llvm/llvm-project/pull/149823