fix: simplicity-sys is skipped in CI

simplicity-sys unit tests are not run if simplicity-lang unit tests
fail, even for a unified command like `cargo test --workspace`.

Author: uncomputable

.github/workflows/main.yml

@@ -116,4 +116,6 @@ jobs:
       - name: Set dependencies
         run: cp Cargo-recent.lock Cargo.lock
       - name: Run unit tests
-        run: cargo test --locked --workspace --all-features
+        run: |
+          cargo test --locked --manifest-path simplicity-sys/Cargo.toml
+          cargo test --locked --workspace --all-features