Use the section flag 'o' for __patchable_function_entries

Use the section flag 'o' for __patchable_function_entries

This commit in GNU binutils 2.35:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commit;h=b7d072167715829eed0622616f6ae0182900de3e

added the section flag 'o' to .section directive:

.section __patchable_function_entries,"awo",@progbits,foo

which specifies the symbol name which the section references.  Assembler
creates a unique __patchable_function_entries section with the section,
where foo is defined, as its linked-to section.  Linker keeps a section
if its linked-to section is kept during garbage collection.

This patch checks assembler support for the section flag 'o' and uses
it to implement __patchable_function_entries section.  Since Solaris may
use GNU assembler with Solairs ld.  Even if GNU assembler supports the
section flag 'o', it doesn't mean that Solairs ld supports it.  This
feature is disabled for Solairs targets.

gcc/

	PR middle-end/93195
	PR middle-end/93197
	* configure.ac (HAVE_GAS_SECTION_LINK_ORDER): New.  Define 1 if
	the assembler supports the section flag 'o' for specifying
	section with link-order.
	* output.h (SECTION_LINK_ORDER): New.  Defined to 0x8000000.
	(SECTION_MACH_DEP): Changed from 0x8000000 to 0x10000000.
	* targhooks.c (default_print_patchable_function_entry): Pass
	SECTION_LINK_ORDER to switch_to_section if the section flag 'o'
	works.  Pass current_function_decl to switch_to_section.
	* varasm.c (default_elf_asm_named_section): Use 'o' flag for
	SECTION_LINK_ORDER if assembler supports it.
	* config.in: Regenerated.
	* configure: Likewise.
	* doc/sourcebuild.texi: Document o_flag_in_section.

gcc/testsuite/

	PR middle-end/93195
	* g++.dg/pr93195a.C: New test.
	* g++.dg/pr93195b.C: Likewise.
	* lib/target-supports.exp
	(check_effective_target_o_flag_in_section): New proc.