nested, openmp: Wrap OMP_CLAUSE_*_GIMPLE_SEQ into GIMPLE_BIND for declare_vars [PR108435]

nested, openmp: Wrap OMP_CLAUSE_*_GIMPLE_SEQ into GIMPLE_BIND for declare_vars [PR108435]

When gimplifying OMP_CLAUSE_{LASTPRIVATE,LINEAR}_STMT, we wrap it always
into a GIMPLE_BIND, but when putting statements directly into
OMP_CLAUSE_{LASTPRIVATE,LINEAR}_GIMPLE_SEQ, we do it only if needed (there
are any temporaries that need to be declared in the sequence).
convert_nonlocal_omp_clauses was relying on the GIMPLE_BIND to be there always
because it called declare_vars on it.

The following patch wraps it into GIMPLE_BIND in tree-nested if we need to
declare_vars on it on demand.

2023-02-02  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/108435
	* tree-nested.cc (convert_nonlocal_omp_clauses)
	<case OMP_CLAUSE_LASTPRIVATE>: If info->new_local_var_chain and *seq
	is not a GIMPLE_BIND, wrap the sequence into a new GIMPLE_BIND
	before calling declare_vars.
	(convert_nonlocal_omp_clauses) <case OMP_CLAUSE_LINEAR>: Merge
	with the OMP_CLAUSE_LASTPRIVATE handling except for whether
	seq is initialized to &OMP_CLAUSE_LASTPRIVATE_GIMPLE_SEQ (clause)
	or &OMP_CLAUSE_LINEAR_GIMPLE_SEQ (clause).

	* gcc.dg/gomp/pr108435.c: New test.