mac make: make SDKROOT work on case-sensitive file systems. 
mac make: make SDKROOT work on case-sensitive file systems. 

BUG=http://crbug.com/93635
Review URL: http://codereview.chromium.org/7828093/


witwall/gyp,witwall/gyp,witwall/gyp,witwall/gyp,witwall/gyp