Set EI_OSABI to ELFOSABI_GNU for local IFUNC symbols

Set EI_OSABI to ELFOSABI_GNU for local IFUNC symbols

Since the backend elf_add_symbol_hook isn't called on local symbols,
the EI_OSABI field isn't to ELFOSABI_GNU where are local IFUNC symbols.
This patch changes the x86 backends to set has_gnu_symbols if there are
relocations against IFUNC symbols.  Other backends with IFUNC support
may need a similar change.

This patch also changes the type of has_gnu_symbols from bfd_boolean to
enum elf_gnu_symbols.

bfd/

	PR ld/18815
	* elf-bfd.h (elf_gnu_symbols): New enum.
	(elf_obj_tdata): Use elf_gnu_symbols on has_gnu_symbols.
	* elf-s390-common.c (elf_s390_add_symbol_hook): Set
	has_gnu_symbols to elf_gnu_symbol_any.
	* elf32-arm.c (elf32_arm_add_symbol_hook): Likewise.
	* elf32-m68k.c (elf_m68k_add_symbol_hook): Likewise.
	* elf32-ppc.c (ppc_elf_add_symbol_hook): Likewise.
	* elf32-sparc.c (elf32_sparc_add_symbol_hook): Likewise.
	* elf64-ppc.c (ppc64_elf_add_symbol_hook): Likewise.
	* elf64-sparc.c (elf64_sparc_add_symbol_hook): Likewise.
	* lfxx-aarch64.c (_bfd_aarch64_elf_add_symbol_hook): Likewise.
	* elf32-i386.c (elf_i386_check_relocs): Update has_gnu_symbols
	if there are relocations against IFUNC symbols.
	(elf_i386_add_symbol_hook): Don't check STT_GNU_IFUNC here.
	* elf64-x86-64. (elf_x86_64_check_relocs): Update has_gnu_symbols
	if there are relocations against IFUNC symbols.
	(elf_x86_64_add_symbol_hook): Don't check STT_GNU_IFUNC here.

ld/testsuite/

	PR ld/18815
	* ld-i386/i386.exp: Run pr18815.
	* ld-x86-64/x86-64.exp: Likewise.
	* ld-i386/pr18815.d: New file.
	* ld-i386/pr18815.s: Likewise.
	* ld-x86-64/pr18815.d: Likewise.
	* ld-x86-64/pr18815.s: Likewise.