Fix some references to Makefiles in gyp_skia.

BUG=None
TEST=None, no functional changes. Just updating documentation.
R=epoger@google.com

Review URL: https://codereview.chromium.org/263083006

git-svn-id: http://skia.googlecode.com/svn/trunk@14642 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed