Support NDK r25
Bazel NDK r25 supports needs to use the new Starlark rules of [https://github.com/bazelbuild/rules_android_ndk](https://www.google.com/url?sa=D&q=https%3A%2F%2Fgithub.com%2Fbazelbuild%2Frules_android_ndk).

This PR checks NDK toolchain version and generates proper rules.