* Load AHardwarebuffer API dynamically, so vulkan backend can be
  built with old NDK, but can work with newer android releases.
* Do not link with libvulkan on android.
* Expose EGL_ANDROID_get_native_client_buffer extension with vulkan
  backend.

Bug: chromium:1170339
Change-Id: Idf7f6867a86ae40ba6d57a86e419c610ba404ba8
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2653506Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Peng Huang <penghuang@chromium.org>