am 906269a4: Switch prebuilts/ndk "current" from r8 to r9

* commit '906269a47997164c77938402d9cb3d1bbfdea8a4':
  Switch prebuilts/ndk "current" from r8 to r9
tree: cf0e35cd599127b67cab2e0e5163cd0787ef3a80
  1. 4/
  2. 5/
  3. 6/
  4. 7/
  5. 8/
  6. 9/
  7. Android.mk
  8. CleanSpec.mk