Add a Windows Android NDK asset.

Add a Windows Android NDK asset.

We can build for Android from Windows now.  I intend to add a bot to keep it that way, just like Build-Mac-Clang-arm64-Debug-GN_Android does for Mac.  The Windows Android builder will need this NDK.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4280

DOCS_PREVIEW= https://skia.org/?cl=4280

Change-Id: Ifaeeb9b81822a410bdf79b39c7e66d0765f78e0b
Reviewed-on: https://skia-review.googlesource.com/4280
Reviewed-by: Eric Boren <borenet@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>