Make sure we keep up with mir optimizations (#407)

Author: oli-obk

highfive/configs/rust-lang/rust.json

@@ -201,6 +201,10 @@
             "message": "Some changes occured to the Miri submodule",
             "reviewers": ["@rust-lang/miri"]
         },
+        "compiler/rustc_mir_transform/src/": {
+            "message": "Some changes occured to MIR optimizations",
+            "reviewers": ["@rust-lang/mir-opt"]
+        },
         "library": {
             "message": "Hey! It looks like you've submitted a new PR for the library teams!\n\nIf this PR contains changes to any `rust-lang/rust` public library APIs then please comment with `@rustbot label +T-libs-api -T-libs` to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant [API Change Proposal](https://std-dev-guide.rust-lang.org/feature-lifecycle/api-change-proposals.html) or [create one](https://github.com/rust-lang/libs-team/issues/new?assignees=&labels=api-change-proposal%2C+T-libs-api&template=api-change-proposal.md&title=%28My+API+Change+Proposal%29) if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.\n\nExamples of `T-libs-api` changes:\n\n* Stabilizing library features\n* Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types\n* Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)\n* Changing public documentation in ways that create new stability guarantees\n* Changing observable runtime behavior of library APIs",
             "reviewers": []