Fix internal error when using --emit-relocs with plugins.

Fix internal error when using --emit-relocs with plugins.

When an .eh_frame section has deferred layout because of plugins, gold
was neglecting to mark the section as deferred. When we later processed
the corresponding relocation section, we were then ignoring it, causing
the internal error later on in the link.

gold/
	PR gold/23397
	* object.cc (Sized_relobj_file::do_layout): Mark section as deferred.
	* testsuite/Makefile.am (plugin_test_1): Add --emit-relocs option to
	existing test case.
	* testsuite/Makefile.in: Regenerate.