ci: Fix empty toolchain expression

Author: nonperforming

.github/workflows/launcher.yml

@@ -35,15 +35,16 @@ jobs:
         uses: actions/checkout@v4.2.2
       - name: Setup Rust
         uses: dtolnay/rust-toolchain@b3b07ba8b418998c39fb20f53e8b695cdcc8de1b
+        id: rust
         with:
           toolchain: ${{ matrix.toolchain }}
       - name: Cache dependencies
         uses: Swatinem/rust-cache@9d47c6ad4b02e050fd481d890b2ea34778fd09d6
         with:
-          key: ${{ steps.toolchain.outputs.cachekey }}
+          key: ${{ steps.rust.outputs.cachekey }}
           workspaces: "./Launcher -> target"
       - name: Build
-        run: cargo +${{ steps.toolchain.outputs.name }} build --verbose
+        run: cargo +${{ steps.rust.outputs.name }} build --verbose
       - name: Upload artifact
         uses: actions/upload-artifact@v4.6.2
         with: