Patch merged into coreboot/master: Makefile: Replace the way to test if a string is empty

the following patch was just integrated into master:
commit 46a7c82bcf9418bc12972eb1c54d19c9a98a9e2b
Author: zbao 
Date:   Fri Sep 11 08:49:38 2015 -0400

Makefile: Replace the way to test if a string is empty

The output of command below,
    # i386-elf-nm build/cbfs/fallback/romstage_null.offenders | \
                         grep -q "" ; echo $?
    has different result on MacOS, OS X Mavericks, which outputs 0.
    On linux, it outputs 1.

I assume it is misleading to search an empty string in a empty
    string. Change it to testing if the string is empty.

Change-Id: Ie4b8fe1fb26df092e2985937251a49feadc61eb0
    Signed-off-by: Zheng Bao 
    Signed-off-by: Zheng Bao 
    Reviewed-on: http://review.coreboot.org/11600
    Tested-by: build bot (Jenkins)
    Reviewed-by: Patrick Georgi

See http://review.coreboot.org/11600 for details.

-gerrit