Upload hook that guides people towards AOSP

The canonical location of certain parts of the source tree live in
AOSP, and should not be changed internally to avoid merge conflicts.

WARNING only: The PREUPLOAD script warns developer if the change is
not uploaded on AOSP.

Test: create a CL in master and upload
Change-Id: I9a100d86d31ef35d1f4617c75d523724acf8ae60

PREUPLOAD.cfg

@@ -4,3 +4,6 @@ ignore_merged_commits = true
 [Builtin Hooks]
 clang_format = true
 
+[Hook Scripts]
+aosp_first = ${REPO_ROOT}/frameworks/base/tools/aosp/aosp_sha.sh ${PREUPLOAD_COMMIT} ".*$"
+