gcc/
	* config/darwin.h (TARGET_SYSTEM_ROOT): Remove this from here,
	(HAVE_LD_SYSROOT): New.  (SYSROOT_SPEC): New. 
	(LINK_SYSROOT_SPEC): Revise to remove the default for target sysroot.
	(STANDARD_STARTFILE_PREFIX_1): New.
	(STANDARD_STARTFILE_PREFIX_2): New.

From-SVN: r228950