frameworks/support
is no longer part of the platform checkout. Android platform now uses prebuilts of AndroidX for everything. AndroidX is being developed as an unbundled project.
*-sources.jar
s in prebuilts/sdk/current/androidx
repo init -u https://android.googlesource.com/platform/manifest -b androidx-master-dev
ub-supportlib-master
repo.repo init -u persistent-https://googleplex-android.git.corp.google.com/platform/manifest -b ub-supportlib-master