change gm option from -config to --config, to match the double-dash convention of
all of its other options.
Review URL: https://codereview.appspot.com/6337044

git-svn-id: http://skia.googlecode.com/svn/trunk@4307 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed