Merge "Add documentation about the purpose of #apex and #symbols in map.txt"...

Merge "Add documentation about the purpose of #apex and #symbols in map.txt" am: baef7ff6 am: ac07eef7

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/2393579



Change-Id: I1bcabee26c2b1ff335f514620983941d2178d364
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>