Merge "envsetup.sh: explain _why_ there's an adb function in here." into main...

Merge "envsetup.sh: explain _why_ there's an adb function in here." into main am: 4e1a3498 am: 7a04506d

Original change: https://android-review.googlesource.com/c/platform/build/+/3001072



Change-Id: I3176b8cfb219facbc00043600499e649f6c8538f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>