Update build-tools to ab/3916447 am: 649ab9d7c4  -s ours
am: a39d18d299  -s ours

Change-Id: I0a8fa3bf0ca18c10f8219fabfd8ac79b674fb664
tree: fa7607f1a6931d8c2b67cc23edb59fa05373a83d
  1. darwin-x86/
  2. linux-x86/
  3. build-prebuilts.sh
  4. manifest.xml