openmp: Disallow reduction with var private in containing parallel even on scope...

openmp: Disallow reduction with var private in containing parallel even on scope [PR102504]

The standard has a restriction:
"A list item that appears in a reduction clause of a scope construct must be
shared in the parallel region to which a corresponding scope region binds."
similar to the restriction for worksharing constructs, but we were checking
it only on worksharing constructs and not for scope and ICEd later on during
omp expansion.

2021-09-29  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/102504
	* gimplify.c (gimplify_scan_omp_clauses): Use omp_check_private even
	in OMP_SCOPE clauses, not just on worksharing construct clauses.

	* c-c++-common/gomp/scope-4.c: New test.

(cherry picked from commit d3e7bb15e28c554bf4484a912f3b9c18c60ec68f)