make: Remove stray $(SDKROOT) from -F arguments.
make: Remove stray $(SDKROOT) from -F arguments.

$(SDKROOT) isn't set, so it evaluates to nothing, but not
writing it is, uh, cleaner.

BUG=none
TEST=skia/skia.target.mk no longer contains /Developer/SDKs/MacOSX10.6.sdk/$(SDKROOT)/System/Library/Frameworks/ApplicationServices.framework/Frameworks
Review URL: http://codereview.chromium.org/8606003

csulmone/gyp,csulmone/gyp,csulmone/gyp,csulmone/gyp