Add libcompiler_rt-extras from prebuilts/ndk.

Still not ready to adopt the new static libraries, but we've needed
this for a while now. Copy it into place for now.

These came from the current prebuilts/ndk, which themselves came from
AOSP master build 4567395.

Test: ndk/checkbuild.py && ndk/run_tests.py
Bug: https://github.com/android-ndk/ndk/issues/294
Change-Id: Ia713a957df5c913b36d5f6c8fff35bbb11315ae8
(cherry picked from commit bbdeccffb3267f8ae9422d6f7ed9fe33d25528f0)
6 files changed