[llvm] [openmp] Deprecate LLVM_ENABLE_PROJECTS in favor of LLVM_ENABLE_RUNTIMES (PR #124711)

[Ye Luo via llvm-commits]

ye-luo wrote:

> > > Flang currently only works with `LLVM_ENABLE_PROJECTS=openmp`:
> > 
> > 
> > I'm afraid this is not true in the first place. My nightly tests builds openmp as runtime and I'm using flang+openmp to test my applications.
> 
> Where do you get `omp_lib.mod` from?

yeluo at jlselogin7:/soft/compilers/llvm/main-20250129> find -name omp_lib.mod
./include/flang/omp_lib.mod


https://github.com/llvm/llvm-project/pull/124711