Migrate Android NDK to CIPD [1/2] The Android NDK dependency is moving to a CIPD bucket to reduce the checkout cost and to eventually move to NDK v25. This introduces the NDK into an 'android_toolchain' directory. Following the roll of chromium/base in this repository, a second change will delete the old 'android_ndk' checkout. As a result, the checkout size of this repository will temporarily increase. Bug: chromium:1448383 Test: Verified local builds of ANGLE. Change-Id: Id2b7593270ae8d98e7353011dbc1b564da107786 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4585388 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>