Update git submodules

* Update ndk from branch 'ndk-release-r18'
  to ed20dd9dd6b153bd13d412ad4a6843bd74fcd0cb
  - Merge "ndk-which: require exact ABI strings" into ndk-release-r18
  - ndk-which: require exact ABI strings
    
    e.g. Allow x86, but not x86-foo or foo-x86.
    
    Bug: android/ndk#755
    Bug: android/ndk#56
    Test: `ndk-which --abi x86-foo objdump`
    Test: `ndk-which --abi foo-x86 objdump`
    Change-Id: If9bc43847265be90b432a3cb7b112040580726c8
    (cherry picked from commit d626c3f2673f7e2681eba5090524f49d44cfb429)