[automerger skipped] DO NOT MERGE: Add a soong var that will be used to enable/disable rust am: 09132f63 -s ours am: 513bf6dd

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/modules/DnsResolver/+/13894017

Change-Id: I1dfea461b8d33c9174eaef9315b4134d0fb3a984