Test binutils_assemble return value

Test binutils_assemble return value

This is a followup to "binutils nm testsuite tidy".  Since the perror
in binutils_assemble has been removed, we need to take more care in
failure paths.

The patch also fixed a number of .exp files that have multiple tests,
where an assembly failure returns from the .exp file.  In most cases
it is nicer to attempt all tests.

	* testsuite/binutils-all/ar.exp (unique_symbol): Don't run AR
	if assembly fails.
	* testsuite/binutils-all/arc/objdump.exp (check_assembly): If
	objfile is empty, fail test.
	* testsuite/binutils-all/arm/objdump.exp: Don't return if assembly
	fails for a test, continue on to other tests.
	* testsuite/binutils-all/bfin/objdump.exp: Likewise.
	* testsuite/binutils-all/hppa/objdump.exp: Likewise.
	* testsuite/binutils-all/m68k/objdump.exp: Likewise.
	* testsuite/binutils-all/vax/objdump.exp: Likewise.
	* testsuite/binutils-all/size.exp: Likewise.
	* testsuite/binutils-all/nm.exp: Likewise.  Move PR12753 test.
	* testsuite/binutils-all/objcopy.exp: Don't perror on assembly fail.
	* testsuite/binutils-all/objdump.exp: Report assembly fails.