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 addressed, this commit can be reverted.
Refs: https://github.com/nodejs/build/issues/3204#issuecomment-1550411656