Add Trusty rules.mk for libfdt am: 159d7b1955

Original change: https://android-review.googlesource.com/c/platform/external/dtc/+/1976531

Change-Id: If0dd2840226bb63002087a13b8b7a61a634844bc
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>