Adding autogenerated Trusty makefile rules am: 78719f0d4f am: 035dd3df19

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/syn/+/2751073

Change-Id: I8470ee5d7be3009d6a5331f16aaebb9193621d5b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>