Auto merge of #15714 - lnicola:rust-bors, r=lnicola

minor: Prepare for rust-bors

This [only works](https://rust-lang.zulipchat.com/#narrow/stream/242791-t-infra/topic/testing.20new.20bors.20implementation/near/395026488) for try builds at the moment, unfortunately.

Author: bors

.github/workflows/ci.yaml

@@ -8,6 +8,7 @@ on:
     branches:
       - auto
       - try
+      - automation/bors/try
 
 env:
   CARGO_INCREMENTAL: 0

rust-bors.toml

@@ -0,0 +1 @@
+timeout = 3600