Fix packages for Android R SDK.

Include build-tools 30.0.1 which is also needed by the R SDK.

The Android R SDK sources aren't available yet as R has not been
released to AOSP. Disable updating the sources package for now.

Bug: 1106471
Change-Id: I2ec942069f3ca95c694be0cbf3510700afcd1b19
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2304533
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Garrett Beaty <gbeaty@chromium.org>
Commit-Queue: Richard Coles <torne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#789544}
GitOrigin-RevId: 91d31860db8da994a83895cdb1c93e5563080d7b