ci: Enable WASM build for XCM integration tests

The integration tests require WASM binaries for westend-runtime and
asset-hub-westend-runtime. Override SKIP_WASM_BUILD=0 specifically
for the integration test step.

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: bkontur

.github/workflows/check.yml

@@ -145,6 +145,11 @@ jobs:
       - name: Run (Westend) runtime tests
         run: |
           cargo test -p bulletin-westend-runtime
+
+      - name: Run (Westend) XCM integration tests
+        env:
+          SKIP_WASM_BUILD: 0
+        run: |
           cargo test -p bulletin-westend-integration-tests
 
       # TODO: check benchmarks