ld: Add LTO and none-LTO output support for ld -r

ld: Add LTO and none-LTO output support for ld -r

Link with mixed IR/non-IR objects

* 2 kinds of object files
  o non-IR object file has
    * non-IR sections
  o IR object file has
    * IR sections
    * non-IR sections
    * The output of "ld -r" with mixed IR/non-IR objects should work with:
        o Compilers/linkers with IR support.
	o Compilers/linkers without IR support.
* Add the mixed object file which has
  o IR sections
  o non-IR sections:
    * Object codes from IR sections.
    * Object codes from non-IR object files.
  o Object-only section:
    * With section name ".gnu_object_only" and SHT_GNU_OBJECT_ONLY type
    on ELF:
    https://gitlab.com/x86-psABIs/Linux-ABI
    #define SHT_GNU_OBJECT_ONLY 0x6ffffff8	/* Object only */
    * Contain non-IR object file.
    * Input is discarded after link.
* Linker action:
  o Classify each input object file:
    * If there is a ".gnu_object_only" section, it is a mixed object file.
    * If there is a IR section, it is an IR object file.
    * Otherwise, it is a non-IR object file.
  o Relocatable non-IR link:
    * Prepare for an object-only output.
    * Prepare for a regular output.
    * For each mixed object file:
      * Add IR and non-IR sections to the regular output.
      * For object-only section:
	* Extract object only file.
	* Add it to the object-only output.
	* Discard object-only section.
    * For each IR object file:
      * Add IR and non-IR sections to the regular output.
    * For each non-IR object file:
      * Add non-IR sections to the regular output.
      * Add non-IR sections to the object-only output.
    * Final output:
      * If there are IR objects, non-IR objects and the object-only
      output isn't empty:
	* Put the object-only output into the object-only section.
	* Add the object-only section to the regular output.
	* Remove the object-only output.
  o Normal link and relocatable IR link:
    * Prepare for output.
    * IR link:
      * For each mixed object file:
	* Compile and add IR sections to the output.
	* Discard non-IR sections.
	* Object-only section:
	  * Extract object only file.
	  * Add it to the output.
	  * Discard object-only section.
      * For each IR object file:
        * Compile and add IR sections to the output.
	* Discard non-IR sections.
      * For each non-IR object file:
	* Add non-IR sections to the output.
    * Non-IR link:
      * For each mixed object file:
	* Add non-IR sections to the output.
	* Discard IR sections and object-only section.
      * For each IR object file:
	* Add non-IR sections to the output.
	* Discard IR sections.
      * For each non-IR object file:
	* Add non-IR sections to the output.

This is useful for Linux kernel build with LTO.

bfd/

	PR ld/12291
	PR ld/12430
	PR ld/13298
	* bfd.c (bfd_lto_object_type): Add lto_mixed_object.
	(bfd): Add object_only_section.
	(bfd_group_signature): New.
	* elf.c (special_sections_g): Add .gnu_object_only.
	* format.c: Include "plugin-api.h" and "plugin.h" if
	BFD_SUPPORTS_PLUGINS is defined.
	(bfd_set_lto_type): Set type to lto_mixed_object for
	GNU_OBJECT_ONLY_SECTION_NAME section.
	(bfd_check_format_matches): Don't check the plugin target twice
	if the plugin target is explicitly specified.
	* opncls.c (bfd_extract_object_only_section): New.
	* plugin.c (bfd_plugin_fake_text_section): New.
	(bfd_plugin_fake_data_section): Likewise.
	(bfd_plugin_fake_bss_section): Likewise.
	(bfd_plugin_fake_common_section): Likewise.
	(bfd_plugin_get_symbols_in_object_only): Likewise.
	* plugin.c (add_symbols): Call
	bfd_plugin_get_symbols_in_object_only and count
	plugin_data->object_only_nsyms.
	(bfd_plugin_get_symtab_upper_bound): Count
	plugin_data->object_only_nsyms.
	bfd_plugin_get_symbols_in_object_only and add symbols from
	object only section.
	(bfd_plugin_canonicalize_symtab): Remove fake_section,
	fake_data_section, fake_bss_section and fake_common_section.
	Set udata.p to NULL.  Use bfd_plugin_fake_text_section,
	bfd_plugin_fake_data_section, bfd_plugin_fake_bss_section and
	bfd_plugin_fake_common_section.
	Set udata.p to NULL.
	* plugin.h (plugin_data_struct): Add object_only_nsyms and
	object_only_syms.
	* section.c (GNU_OBJECT_ONLY_SECTION_NAME): New.
	* bfd-in2.h: Regenerated.

binutils/

	PR ld/12291
	PR ld/12430
	PR ld/13298
	* objcopy.c (group_signature): Removed.
	(is_strip_section): Replace group_signature with
	bfd_group_signature.
	(setup_section): Likewise.
	* readelf.c (get_os_specific_section_type_name): Handle
	SHT_GNU_OBJECT_ONLY.

gas/

	PR ld/12291
	PR ld/12430
	PR ld/13298
	* testsuite/gas/elf/section9.s: Add the .gnu_object_only test.
	* testsuite/gas/elf/section9.d: Updated.

include/

	PR ld/12291
	PR ld/12430
	PR ld/13298
	* elf/common.h (SHT_GNU_OBJECT_ONLY): New.

ld/

	PR ld/12291
	PR ld/12430
	PR ld/13298
	* ld.h (ld_config_type): Add emit_gnu_object_only and
	emitting_gnu_object_only.
	* ldelf.c (orphan_init_done): Make it file scope.
	(ldelf_place_orphan): Rename hold to orig_hold.  Initialize hold
	from orig_hold at run-time.
	(ldelf_finish): New.
	* ldelf.h (ldelf_finish): New.
	* ldexp.c (ldexp_init): Take a bfd_boolean argument to supprt
	object-only output.
	(ldexp_finish): Likewise.
	* ldexp.h (ldexp_init): Take a bfd_boolean argument.
	(ldexp_finish): Likewise.
	* ldfile.c (ldfile_try_open_bfd): Call
	cmdline_check_object_only_section.
	* ldlang.c: Include "ldwrite.h" and elf-bfd.h.
	* ldlang.c (cmdline_object_only_file_list): New.
	(cmdline_object_only_archive_list): Likewise.
	(cmdline_temp_object_only_list): Likewise.
	(cmdline_lists_init): Likewise.
	(cmdline_list_new): Likewise.
	(cmdline_list_append): Likewise.
	(print_cmdline_list): Likewise.
	(cmdline_on_object_only_archive_list_p): Likewise.
	(cmdline_object_only_list_append): Likewise.
	(cmdline_get_object_only_input_files): Likewise.
	(cmdline_arg): Likewise.
	(setup_section): Likewise.
	(copy_section): Likewise.
	(cmdline_fopen_temp): Likewise.
	(cmdline_add_object_only_section): Likewise.
	(cmdline_emit_object_only_section): Likewise.
	(cmdline_extract_object_only_section): Likewise.
	(cmdline_check_object_only_section): Likewise.
	(cmdline_remove_object_only_files): Likewise.
	(lang_init): Take a bfd_boolean argument to supprt object-only
	output.  Call cmdline_lists_init.
	(load_symbols): Call cmdline_on_object_only_archive_list_p
	to check if an archive member should be loaded.
	(lang_process): Handle object-only link.
	* ldlang.h (lang_init): Take a bfd_boolean argument.
	(cmdline_enum_type): New.
	(cmdline_header_type): Likewise.
	(cmdline_file_type): Likewise.
	(cmdline_bfd_type): Likewise.
	(cmdline_union_type): Likewise.
	(cmdline_list_type): Likewise.
	(cmdline_emit_object_only_section): Likewise.
	(cmdline_check_object_only_section): Likewise.
	(cmdline_remove_object_only_files): Likewise.
	* ldmain.c (main): Call xatexit with
	cmdline_remove_object_only_files.  Pass FALSE to lang_init,
	ldexp_init and ldexp_finish.  Use ld_parse_linker_script.
	Set link_info.output_bfd to NULL after close.  Call
	cmdline_emit_object_only_section if needed.
	(add_archive_element): Call cmdline_check_object_only_section.
	(ld_parse_linker_script): New.
	* ldmain.h (ld_parse_linker_script): New.
	* plugin.c (plugin_maybe_claim): Call
	cmdline_check_object_only_section on claimed IR files.
	* scripttempl/elf.sc: Also discard .gnu_object_only sections.
	* scripttempl/elf64hppa.sc: Likewise.
	* scripttempl/elfxtensa.sc: Likewise.
	* scripttempl/mep.sc: Likewise.
	* scripttempl/pe.sc: Likewise.
	* scripttempl/pep.sc: Likewise.
	* emultempl/aarch64elf.em (gld${EMULATION_NAME}_finish): Replace
	finish_default with ldelf_finish.
	* emultempl/alphaelf.em (alpha_finish): Likewise.
	* emultempl/avrelf.em (avr_finish): Likewise.
	* emultempl/elf.em (ld_${EMULATION_NAME}_emulation): Likewise.
	* emultempl/ppc32elf.em (ppc_finish): Likewise.
	* emultempl/ppc64elf.em (gld${EMULATION_NAME}_finish): Likewise.
	* emultempl/spuelf.em (gld${EMULATION_NAME}_finish): Likewise.
	* testsuite/ld-plugin/lto-10.out: New file.
	* testsuite/ld-plugin/lto-10a.c: Likewise.
	* testsuite/ld-plugin/lto-10b.c: Likewise.
	* testsuite/ld-plugin/lto-10r.d: Likewise.
	* testsuite/ld-plugin/lto-4.out: Likewise.
	* testsuite/ld-plugin/lto-4a.c: Likewise.
	* testsuite/ld-plugin/lto-4b.c: Likewise.
	* testsuite/ld-plugin/lto-4c.c: Likewise.
	* testsuite/ld-plugin/lto-4r-a.d: Likewise.
	* testsuite/ld-plugin/lto-4r-b.d: Likewise.
	* testsuite/ld-plugin/lto-4r-c.d: Likewise.
	* testsuite/ld-plugin/lto-4r-d.d: Likewise.
	* testsuite/ld-plugin/lto.exp (lto_link_tests): Prepare for
	"LTO 4[acd]", "lto-4r-[abcd]" and "LTO 10" tests.
	(lto_run_tests): Add "LTO 4[acd]" and "LTO 10" tests.
	Build liblto-4.a.  Run "lto-4r-[abcd]" tests.
	Run lto-10r and create tmpdir/lto-10.o.
	Add test for nm on mixed LTO/non-LTO object.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>