re PR target/48108 (lto should be containerized in a single mach-o section on darwin)

re PR target/48108 (lto should be containerized in a single mach-o section on darwin)

gcc:

	PR target/48108
	Backport from mainline r180523
	* config/darwin.c (top level): Amend comments concerning LTO output.
	(lto_section_num): New variable.  (darwin_lto_section_e): New GTY.
	(LTO_SECTS_SECTION, LTO_INDEX_SECTION): New.
	(LTO_NAMES_SECTION): Rename.
	(darwin_asm_named_section): Record LTO section counts and switches
	in a vec of darwin_lto_section_e.
	(darwin_file_start): Remove unused code.
	(darwin_file_end): Put an LTO section termination label.  Handle
	output of the wrapped LTO sections, index and names table.

libiberty:

	PR target/48108
	Backport from mainline r180523
	* simple-object-mach-o.c  (GNU_WRAPPER_SECTS, GNU_WRAPPER_INDEX,
	GNU_WRAPPER_NAMES): New macros.
	(simple_object_mach_o_segment): Handle wrapper scheme.
	(simple_object_mach_o_write_section_header): Allow the segment name
	to be supplied.
	(simple_object_mach_o_write_segment): Handle wrapper scheme.  Ensure
	that the top-level segment name in the load command is empty.
	(simple_object_mach_o_write_to_file): Determine the number of
	sections during segment output, use that in writing the header.

From-SVN: r181336