XPLINK considerations

A nested enclave situation where the parent enclave is running in an XPLINK(OFF) environment and the child enclave requires XPLINK(ON) is not supported. A parent enclave running XPLINK(ON) will support a nested child enclave of either XPLINK(ON) or XPLINK(OFF). In the latter case, the application in the child enclave will go through compatibility glue code when calling the C RTL (that is, the child enclave will run with an environment with the XPLINK runtime option forced ON).