test: skip mutable-global-sharing v128 tests on s390x

Author: guybedford

test/parallel/test-wasm-simd-global.js

@@ -17,5 +17,15 @@ try {
 if (supportsSimd) {
   const runner = new WPTRunner('wasm/jsapi');
   runner.setFlags(['--experimental-wasm-modules']);
+
+  // v128 SIMD globals are broken on s390x due to a V8 big-endian bug.
+  if (process.arch === 's390x') {
+    for (const spec of runner.specs) {
+      if (spec.filename === 'esm-integration/mutable-global-sharing.tentative.any.js') {
+        spec.skipReasons.push('v128 SIMD globals broken on s390x due to V8 big-endian bug');
+      }
+    }
+  }
+
   runner.runJsTests();
 }