test: skip experimental test with pointer compression

The test test/parallel/test-experimental-shared-value-conveyor.js was
added to test the --harmony-struct feature of V8. However, when used
with pointer compression, the process crashes. This commit skips
the test for pointer compression builds. This change uses a child
process because starting a Node pointer compression build with
--harmony-struct immediately crashes the process. Once this crash
is addresses, this commit can be reverted.

PR-URL: #48738
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Debadree Chatterjee <debadree333@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>

test/parallel/test-experimental-shared-value-conveyor.js

@@ -1,25 +1,38 @@
 'use strict';
-
-// Flags: --harmony-struct
-
 const common = require('../common');
 const assert = require('assert');
+const { spawnSync } = require('child_process');
 const { Worker, parentPort } = require('worker_threads');
 
-// Do not use isMainThread so that this test itself can be run inside a Worker.
-if (!process.env.HAS_STARTED_WORKER) {
-  process.env.HAS_STARTED_WORKER = 1;
-  const m = new globalThis.SharedArray(16);
+if (process.env.TEST_CHILD_PROCESS === '1') {
+  // Do not use isMainThread so that this test itself can be run inside a Worker.
+  if (!process.env.HAS_STARTED_WORKER) {
+    process.env.HAS_STARTED_WORKER = 1;
+    const m = new globalThis.SharedArray(16);
 
-  const worker = new Worker(__filename);
-  worker.once('message', common.mustCall((message) => {
-    assert.strictEqual(message, m);
-  }));
+    const worker = new Worker(__filename);
+    worker.once('message', common.mustCall((message) => {
+      assert.strictEqual(message, m);
+    }));
 
-  worker.postMessage(m);
+    worker.postMessage(m);
+  } else {
+    parentPort.once('message', common.mustCall((message) => {
+      // Simple echo.
+      parentPort.postMessage(message);
+    }));
+  }
 } else {
-  parentPort.once('message', common.mustCall((message) => {
-    // Simple echo.
-    parentPort.postMessage(message);
-  }));
+  if (process.config.variables.v8_enable_pointer_compression === 1) {
+    common.skip('--harmony-struct cannot be used with pointer compression');
+  }
+
+  const args = ['--harmony-struct', __filename];
+  const options = { env: { TEST_CHILD_PROCESS: '1', ...process.env } };
+  const child = spawnSync(process.execPath, args, options);
+
+  assert.strictEqual(child.stderr.toString().trim(), '');
+  assert.strictEqual(child.stdout.toString().trim(), '');
+  assert.strictEqual(child.status, 0);
+  assert.strictEqual(child.signal, null);
 }