binutils nm testsuite tidy

binutils nm testsuite tidy

We can run the gnu_unique_object symbol test  on all ELF targets.
Those that don't support the symbol type and fail to assemble can just
be resolved as "unsupported".  This means binutils_assemble can't
report an error on assembly failure, but it probably should never have
done that anyway.

	* testsuite/lib/utils-lib.exp (default_binutils_assemble_flags):
	Don't perror on assembler diagnostic output.
	* testsuite/binutils-all/nm.exp: Run unique symbol test on all
	ELF targets.  Resolve as "unsupported" on assembly failure.