[llvm] [openmp] [openmp][wasm] Allow compiling OpenMP to WebAssembly (PR #71297)

[Johannes Doerfert via llvm-commits]

jdoerfert wrote:

> This change allows building the static OpenMP runtime, libomp.a, as WebAssembly.
If you are planning to use LTO across the user code and runtime we need to disable certain parts of OpenMP-Opt or bad things might happen.

https://github.com/llvm/llvm-project/pull/71297