[clang] [OpenMP] Allow OMP6.0 features. (PR #122108)

[Michael Kruse via cfe-commits]

Meinersbur wrote:

> In #119891 we are introducing the support for `#pragma omp stripe` which is an OMP6.0 feature (see [#119891 (files)](https://github.com/llvm/llvm-project/pull/119891/files#r1896944800)). This PR changes the default option to 6.0.

Summary (which usually is the basis for the commit message) needs an update.

Suggestion:
Add support for the `-fopenmp-version=60` command line argument. It is needed for #122108 (`#pragma omp stripe`) which will be the first OpenMP 6.0 directive implemented. Add regression tests for Clang in `-fopenmp-version=60` mode.

https://github.com/llvm/llvm-project/pull/122108