disable gammatext gm for a while, looking for other flakes

BUG=skia:

Review URL: https://codereview.chromium.org/725303002
Fix Android framework build.

When we define SK_BUILD_FOR_ANDROID, we don't define it to anything,
so

    #if SK_BUILD_FOR_ANDROID

is not a meaningful check. Instead, use #ifdef.

TBR=caryclark@google.com, djsollen@google.com

Review URL: https://codereview.chromium.org/728013002