Add objcopy stage between assembly and linking for run_dump_test

ld/testsuite/

	* lib/ld-lib.exp: Add objcopy_objects command to run_dump_test.
	This allows each input object to be optionally run through
	objcopy before linking.
ld: Split GENSCRIPTS rule from dependencies to fix tdir_'s.

	* Makefile.am: Change all rules with ${GENSCRIPTS}
	invocations to be just dependencies.
	($(ALL_EMULATION_SOURCES) $(ALL_64_EMULATION_SOURCES))
	(run-genscripts): New rules.
	* Makefile.in: Regenerate.