ld: Set non_ir_ref_regular on symbols referenced in regular objects

ld: Set non_ir_ref_regular on symbols referenced in regular objects

If linker plugin is enabled, set non_ir_ref_regular on symbols referenced
in regular objects so that linker plugin will get the correct symbol
resolution.

bfd/

	PR ld/22502
	* elflink.c (_bfd_elf_merge_symbol): Also skip definition from
	an IR object.
	(elf_link_add_object_symbols): If linker plugin is enabled, set
	non_ir_ref_regular on symbols referenced in regular objects so
	that linker plugin will get the correct symbol resolution.

ld/

	PR ld/22502
	* testsuite/ld-plugin/lto.exp: Run PR ld/22502 test.
	* testsuite/ld-plugin/pr22502a.c: New file.
	* testsuite/ld-plugin/pr22502b.c: Likewise.