Switch to a new section if the SECTION_RETAIN bit doesn't match

Switch to a new section if the SECTION_RETAIN bit doesn't match

When definitions marked with used attribute and unmarked definitions are
placed in the section with the same name, switch to a new section if the
SECTION_RETAIN bit doesn't match.

gcc/

	PR target/98146
	* output.h (switch_to_section): Add a tree argument, default to
	nullptr.
	* varasm.c (get_section): If the SECTION_RETAIN bit doesn't match,
	return and switch to a new section later.
	(assemble_start_function): Pass decl to switch_to_section.
	(assemble_variable): Likewise.
	(switch_to_section): If the SECTION_RETAIN bit doesn't match,
	switch to a new section.

gcc/testsuite/

	PR target/98146
	* c-c++-common/attr-used-5.c: New test.
	* c-c++-common/attr-used-6.c: Likewise.
	* c-c++-common/attr-used-7.c: Likewise.
	* c-c++-common/attr-used-8.c: Likewise.
	* c-c++-common/attr-used-9.c: Likewise.