x86: Remove the unused _GLOBAL_OFFSET_TABLE_

x86: Remove the unused _GLOBAL_OFFSET_TABLE_

Since _GLOBAL_OFFSET_TABLE_ may be referenced implicitly on x86,
checking ref_regular_nonweak leaves the unused _GLOBAL_OFFSET_TABLE_
in output.  This patch checks explicit GOT references instead.

ld-i386/discarded1.s and ld-x86-64/discarded1.s are updated to avoid
linker optimization which removes GOT references.

bfd/

	PR ld/22782
	* elf32-i386.c (elf_i386_check_relocs): Set got_referenced if
	_GLOBAL_OFFSET_TABLE_ is referenced or GOT is needed to resolve
	undefined weak symbol to 0.
	* elf64-x86-64.c (elf_x86_64_check_relocs): Set got_referenced
	if _GLOBAL_OFFSET_TABLE_ is referenced.
	* elfxx-x86.c (_bfd_x86_elf_size_dynamic_sections): Check
	got_referenced instead of ref_regular_nonweak.  Remove the
	unused _GLOBAL_OFFSET_TABLE_ from symbol table.
	* elfxx-x86.h (elf_x86_link_hash_table): Add got_referenced.

ld/

	PR ld/22782
	* testsuite/ld-i386/discarded1.s: Replace mov with div.
	* testsuite/ld-x86-64/discarded1.s: Likewise.
	* testsuite/ld-i386/i386.exp: Run pr22782.
	* testsuite/ld-i386/load1-nacl.d: Updated for removing
	_GLOBAL_OFFSET_TABLE_ from output.
	* testsuite/ld-i386/load1.d: Likewise.
	* testsuite/ld-x86-64/load1a-nacl.d: Likewise.
	* testsuite/ld-x86-64/load1a.d: Likewise.
	* testsuite/ld-x86-64/load1b-nacl.d: Likewise.
	* testsuite/ld-x86-64/load1b.d: Likewise.
	* testsuite/ld-i386/pr22782.d: New file.
	* testsuite/ld-i386/pr22782.s: Likewise.
	* testsuite/ld-x86-64/pr22782.s: Likewise.
	* testsuite/ld-x86-64/pr22782a.d: Likewise.
	* testsuite/ld-x86-64/pr22782b.d: Likewise.
	* testsuite/ld-x86-64/x86-64.exp: Run pr22782a and pr22782b.