Add dirgroup for trusty genrule am: 44b6f30e10 am: a9efe0d71e

Original change: https://android-review.googlesource.com/c/platform/external/libcxx/+/3304097

Change-Id: Ibc3234040226ce3d82f0feade347a3747906d811
Signed-off-by: Automerger Merge Worker <[email protected]>