add a return type to test function used by xcompile

This fixes a minor bug that could cause testcc to fail unexpectedly.

Change-Id: Ib75d343104b6937682c05acf5232596aac83f105
Signed-off-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: http://review.coreboot.org/2068
Tested-by: build bot (Jenkins)
1 file changed