[automerger skipped] DO NOT MERGE: Add a soong var that will be used to...

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

am skip reason: subject contains skip directive

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

Change-Id: I4d73a7d34a993949d7bf036cc95ea67a5e514f1c