Roll NDK to r21d

Bug: skia:10370

In android_ndk_windows/create.py, remove the code to remove a directory.
This directory did not exist when I ran the script, leading to an
Exception.

Change-Id: I91aad3ff3738af99d425d334a11b6c60765e1c11
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/298501
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Derek Sollenberger <djsollen@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
7 files changed