When freezing framework manifests, use aosp_arm64 target am: 6ac1197a06

Original change: https://android-review.googlesource.com/c/platform/system/libhidl/+/2256181

Change-Id: I37de26fe3c3ef9e3a7cf7d9945b185b9a4290ffd
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>