GitLab

- Rename Android sampleApp target to SampleAppAndroid to avoid name collision
- Detect skia_os on Darwin to differentiate between xcode and make builds
Review URL: https://codereview.appspot.com/6303044

git-svn-id: http://skia.googlecode.com/svn/trunk@4168 2bbb7eff-a529-9590-31e7-b0007b416f81