Bootstrap Rust in release jobs.

crates/bds-ui/tests/packaging_assets.rs

@@ -143,6 +143,13 @@ fn tagged_releases_are_built_and_packaged_with_rust_tools() {
             "release workflow must not use host tool {forbidden}"
         );
     }
+    assert_eq!(
+        workflow
+            .matches("actions-rust-lang/setup-rust-toolchain@v1")
+            .count(),
+        4,
+        "every release job using the Ubuntu runner image must bootstrap Rust"
+    );
 
     let linux_dependencies =
         fs::read_to_string(workspace.join(".gitea/scripts/install-linux-build-dependencies.sh"))