Add support for the `-fopenmp-version=60` command line argument. It is
needed for https://github.com/llvm/llvm-project/pull/119891 (`#pragma
omp stripe`) which will be the first OpenMP 6.0 directive implemented.
Add regression tests for Clang in `-fopenmp-version=60` mode.
Added codegen for `omp error` directive.
This is to generate IR to call:
void __kmpc_error(ident_t *loc, int severity, const char *message);
Differential Revision: https://reviews.llvm.org/D139166