Darwin: Update specs handling '-r'.

We were not wrapping all the default libraries in checks for whether
they should be used.  We were also wasting a process launch calling
dsymutil for 'r' link lines (a NOP in practice).  Order the checks
that exclude linking from most likely to occur, downwards.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>

gcc/ChangeLog:

	* config/darwin.h (LINK_COMMAND_SPEC_A): Update 'r' handling to
	skip gomp and itm when r or nodefaultlibs is given.
	(DSYMUTIL_SPEC): Do not call dsymutil for '-r' link lines.
	Update ordering of exclusions, remove duplicate 'v' addition
	(collect2 will add this from the main command line).
1 file changed