Disable Goma for ChromeOS build

Doesn't work on VMs.
(RunBuilders:Build-Ubuntu12-GCC-x86-Debug-Alex,Build-Ubuntu12-GCC-x86-Release-Alex)

R=djsollen@google.com

Review URL: https://codereview.chromium.org/17688005

git-svn-id: http://skia.googlecode.com/svn/trunk@9754 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed