[clang] [llvm] [clang] Implement pragma clang section on COFF targets (PR #112714)

[Reid Kleckner via cfe-commits]

https://github.com/rnk commented:

This is an LLVM code change, not a clang code change. It's an important principle that we test LLVM at the smallest reasonable granularity. Can you replace the clang test with an IR test? I'm sure we already have existing IR carrying existing sections, we just need to test it with a new target.

https://github.com/llvm/llvm-project/pull/112714