Use cpython3 host prebuilts on most branches am: 79299d14bb am: 5313503dd3

Original change: https://android-review.googlesource.com/c/platform/prebuilts/build-tools/+/1535595

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I6be6b791f831a722d2ee4efaa9750353a58b0597