Fix path appending in copy_extra_files am: 20c3738752

Original change: https://googleplex-android-review.googlesource.com/c/platform/external/python/cpython3/+/38396977

Change-Id: If41847826ccaf98d599d5788dfc4ddd27a5a08d5
Signed-off-by: Automerger Merge Worker <[email protected]>