Install target with rustup. (#420)

Signed-off-by: Josh Matthews <[email protected]>

Author: jdm

.github/workflows/main.yml

@@ -34,6 +34,9 @@ jobs:
       - name: rustfmt
         run: cargo fmt --check
 
+      - name: rustup target install
+        run: rustup target add '${{ matrix.platform.target }}'
+
       - name: clippy
         uses: servo/actions/cargo-annotation@main
         with: