This replaces the use of nm to search for the LTO common symbol marker
and uses simple object to see if there's a section starting with
".gnu.lto_." or ".gnu.offload_lto_"

2018-12-23  Iain Sandoe  <iain@sandoe.co.uk>

	* collect2.c (maybe_run_lto_and_relink): Don’t say we have a temp file
	unless we actually did some LTO.
	(has_lto_section, is_lto_object_file): New.
	(maybe_lto_object_file): Remove.
	(scan_prog_file): Use is_lto_object_file() instead of scanning the
	output of nm.

From-SVN: r267371