Update NDK to r21. am: 3724f77b85 am: b5be682234 am: fe88ccdda6 am: 7f5dadb103
Update NDK to r21. am: 3724f77b85 am: b5be682234 am: fe88ccdda6 am: 7f5dadb103

Original change: https://android-review.googlesource.com/c/platform/external/perfetto/+/1500170

Change-Id: If76ac34aca1959d06b084d3237037625fca437cf

google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto