Calling spawn with an invalid path causes .spawn to never return

[Tyriar]

VS Code issues:

• Terminals launched with invalid paths hang during creation and never emit onExit vscode#31301
• Terminal launch errors are not reported properly on Windows vscode#31770

[Tyriar]

Struggling to reproduce the hanging call in node-pty 😕. The following test ends up calling the same native API but throws a Node.js exception just fine:

  describe('WindowsTerminal', () => {
    describe('constructor', () => {
      describe('given an invalid launch path', () => {
        it('should fail gracefully', () => {
          // const term = new WindowsTerminal('');
          // const term = new WindowsTerminal('some_file_not_on_the_path');
          const term = new WindowsTerminal('C:\\WINDOWS\\System32', '', {
            name: "System32",
            cwd: "C:\\Users\\daimms.REDMOND\\Documents\\playground\\t",
          });
        });
      });
    });
  });

  23 passing (552ms)
  1 failing

  1) WindowsTerminal constructor given an invalid launch path should fail gracefully:
     Error: File not found: C:\WINDOWS\System32
      at new WindowsPtyAgent (lib\windowsPtyAgent.js:25:24)
      at new WindowsTerminal (lib\windowsTerminal.js:45:24)
      at Context.<anonymous> (lib\windowsTerminal.test.js:16:32)

[Tyriar]

One way to be sure about this is to use which #112 and validate this on the JS side. One perk here is a lot of C++ code can be removed from path_utils.cc