darwin.h (ASM_SPEC): Simplify.

darwin.h (ASM_SPEC): Simplify.

	* config/i386/darwin.h (ASM_SPEC): Simplify.
	(SUBTARGET_EXTRA_SPECS): Add darwin_subarch spec.
	* config/rs6000/darwin.h (DARWIN_SUBARCH_SPEC): New.
	(SUBTARGET_EXTRA_SPECS): Add darwin_subarch spec.
	* config/darwin.h (LINK_COMMAND_SPEC): Don't pass -arch here.
	(LINK_SPEC): Do pass -arch here.  Handle -force_cpusubtype_ALL
	in all cases.  Pass the right -arch or -arch_only based on -mcpu.
	(ASM_SPEC): Handle -force_cpusubtype_ALL.
	* doc/invoke.texi (Darwin Options): Improve documentation for
	Darwin linker (and libtool) switches.

From-SVN: r89877