Android: Add support for NDK r17

The `armeabi` ABI is no longer available, so we can no longer use it by
default unconditionally.  Instead detect all available ABIs and choose
the oldest arm ABI that is available.

Also update the test suite to account for the lack of `armeabi` support
and pass as of Android NDK r17-beta2.
14 jobs for android-ndk-r17