c++: Avoid strict_aliasing_warning on dependent types or expressions [PR94951]

c++: Avoid strict_aliasing_warning on dependent types or expressions [PR94951]

The following testcase gets a bogus warning during build_base_path,
when cp_build_indirect_ref* calls strict_aliasing_warning with a dependent
expression.  IMHO calling get_alias_set etc. on dependent types feels wrong
to me, we should just defer the warnings in those cases until instantiation
and only handle the cases where neither type nor expr are dependent.

2020-05-06  Jakub Jelinek  <jakub@redhat.com>

	PR c++/94951
	* typeck.c (cp_strict_aliasing_warning): New function.
	(cp_build_indirect_ref_1, build_reinterpret_cast_1): Use
	it instead of strict_aliasing_warning.

	* g++.dg/warn/Wstrict-aliasing-bogus-tmpl.C: New test.