PR105169 Fix references to discarded sections

PR105169 Fix references to discarded sections

When -fpatchable-function-entry= is enabled, certain C++ codes fails to
link because of generated references to discarded sections in
__patchable_function_entry section. This commit fixes this problem by
puting those references in a COMDAT section.

2022-05-06  Giuliano Belinassi  <gbelinassi@suse.de>

gcc/ChangeLog
	PR c++/105169
	* targhooks.cc (default_print_patchable_function_entry_1): Handle COMDAT case.
	* varasm.cc (switch_to_comdat_section): New
	(handle_vtv_comdat_section): Call switch_to_comdat_section.
	* varasm.h: Declare switch_to_comdat_section.

gcc/testsuite/ChangeLog
2022-05-06  Giuliano Belinassi  <gbelinassi@suse.de>

	PR c++/105169
	* g++.dg/modules/pr105169.h: New file.
	* g++.dg/modules/pr105169_a.C: New test.
	* g++.dg/modules/pr105169_b.C: New file.