c++: Use fold_non_dependent_expr rather than maybe_constant_value in...

c++: Use fold_non_dependent_expr rather than maybe_constant_value in __builtin_shufflevector handling [PR106001]

In this case the STATIC_CAST_EXPR expressions in the call aren't
type nor value dependent, but maybe_constant_value still ICEs on those
when processing_template_decl.  Calling fold_non_dependent_expr on it
instead fixes the ICE and folds them to INTEGER_CSTs.

2022-06-17  Jakub Jelinek  <jakub@redhat.com>

	PR c++/106001
	* typeck.cc (build_x_shufflevector): Use fold_non_dependent_expr
	instead of maybe_constant_value.

	* g++.dg/ext/builtin-shufflevector-4.C: New test.