c++: Fix build_omp_array_section for type dependent array_expr [PR118590]

c++: Fix build_omp_array_section for type dependent array_expr [PR118590]

As can be seen on the testcase, when array_expr is type dependent, assuming
it has non-NULL TREE_TYPE is just wrong, it can often have NULL type, and even
if not, blindly assuming it is a pointer or array type is also wrong.

So, like in many other spots in the C++ FE, for type dependent expressions
we want to create something which will survive until instantiation and can be
redone at that point.

Unfortunately, build_omp_array_section is called before we actually do any
kind of checking what array_expr really is, and on invalid code it can be e.g.
a TYPE_DECL on which type_dependent_expression_p ICEs (as can be seen on the
pr67522.C testcase).  So, I've hacked this by checking it is not TYPE_DECL,
I hope a TYPE_P can't make it through there when we just lookup an identifier.

Anyway, this patch is not enough, we can ICE e.g. on __uint128_t[0:something]
during instantiation, so I think something needs to be done for this in pt.cc
as well.

2025-01-23  Jakub Jelinek  <jakub@redhat.com>

	PR c++/118590
	* typeck.cc (build_omp_array_section): If array_expr is type dependent
	or a TYPE_DECL, build OMP_ARRAY_SECTION with NULL type.

	* g++.dg/goacc/pr118590.C: New test.

(cherry picked from commit b02c061bb84c0a2dbf3987e9ff77243d089cbd7a)