Find out whether rust-src rustup component fixes ui test

`cargo test --manifest-path tests/ui/Cargo.toml` is passing locally but
fails in GitHub Actions.

Author: dtolnay

.github/workflows/ci.yml

@@ -52,6 +52,8 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - uses: dtolnay/rust-toolchain@nightly
+        with:
+          components: rust-src
       - name: Enable type layout randomization
         run: echo RUSTFLAGS=${RUSTFLAGS}\ -Zrandomize-layout >> $GITHUB_ENV
       - run: cargo test

rust-toolchain.toml

@@ -0,0 +1,2 @@
+[toolchain]
+components = ["rust-src"]