Make building openmax_dl conditional in gyp.

Intentionally not modifying the GN build.

R=kjellander@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/48479004

Cr-Commit-Position: refs/heads/master@{#8688}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8688 4adac7df-926f-26a2-2b94-8c16560cd09d
3 files changed