Adds arm version and some android configuration build flags.
This adds most of the logic from common.gypi to the Android GN build.
This is currently missing the crtbegin/end stuff and won't actually make real Android builds. The logic in this patch is just the initial conversion that will require testing and several more passes of fixes.
R=torne@chromium.org, torne
Review URL: https://codereview.chromium.org/121173005
git-svn-id: http://src.chromium.org/svn/trunk/src/build@243681 4ff67af0-8c30-449e-8e8b-ad334ec8d88c