[RFA:] fix PR ld/16963, missing SEARCH_DIR for non-sysroot cross-builds

[Alan Modra]

On Tue, May 20, 2014 at 12:48:09AM +0200, Hans-Peter Nilsson wrote:
> There seems to be no reason to have a separate rule for each
> invocation, when using a central rule would suffice.

Only that we've avoided depending on GNU make so far.  I'm not against
the idea, if Nick wants to make that change.

-- 
Alan Modra
Australia Development Lab, IBM