Windows 10 0.11.0-beta hangs on IConptyNative.connect)

[starpit]

Environment details

• OS: Windows
• OS version: 10
• node-pty version: 0.11.0-beta17 and beta18

Issue description

We haven't had a problem with 0.10.0. With 0.11.0 betas on Windows, the conpty bits hang

    if (this._useConpty) {
console.error('######################### 9') // we see this
      const connect = (this._ptyNative as IConptyNative).connect(this._pty, commandLine, cwd, env, c => this._$onProcessExit(c));
      this._innerPid = connect.pid;
console.error('######################### 10') // we don't see this
    }

We get the first printf, but not the second. We get no printfs for _$onProcessExit. We are spawning this from the Electron main process, which hasn't been a problem (and still isn't a problem, on every other platform). I have seen #512 but that user saw the hang on exit, whereas we can't even get the connection established.

Fwiw, the spawned command line is powershell.exe "echo hi"