Add dirgroup for trusty genrule am: 1dfcec3c98

Original change: https://android-review.googlesource.com/c/trusty/app/cast-auth/+/3303740

Change-Id: I833a90ea8bbcacf966c724178eea2e4cbb74bc51
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>