PR28029, debuginfod tests

PR28029, debuginfod tests

binutils/NEWS says of the change in --process-links semantics:
  If other debug section display options are also enabled (eg
  --debug-dump=info) then the contents of matching sections in both the main
  file and the separate debuginfo file *will* be displayed.  This is because in
  most cases the debug section will only be present in one of the files.

Implying that debug info is dumped without --process-links.  Indeed
that appears to be the case for readelf.  This does the same for
objdump.

	PR 28029
	* objdump.c (dump_bfd): Do not exit early when !is_mainfile
	&& !processlinks, instead just exclude non-debug output.
	(dump_dwarf): Add is_mainfile parameter and pass to
	dump_dwarf_section.
	(dump_dwarf_section): Only display debug sections when
	!is_mainfile and !process_links.