objcopy "strip without global symbol" test

This binutils test fails with -fsanitize.  NOSANITIZE_CFLAGS isn't
available in the binutils testsuite, and importing it over from ld
requires a huge amount of tcl code to be moved.  So I chose to simply
add -fno-sanitize=all if -fsanitize= is seem in CFLAGS.

	* testsuite/binutils-all/objcopy.exp
	(objcopy_test_without_global_symbol): Add -fno-sanitize=all to
	flags if -fsanitize= is found in CFLAGS_FOR_TARGET.  Tidy use
	of objfile.