Provide a meaningful error when CWD does not exist

[jugglinmike]

Prior to this commit, if a command was executed in a non-existing current working directory, the "exec" method of the built-in child_process module would throw an error that only partially described the problem, e.g.

Error: spawn /bin/sh ENOENT
    at ChildProcess._handle.onexit (node:internal/child_process:284:19)
    at onErrorNT (node:internal/child_process:477:16)
    at process.processTicksAndRejections (node:internal/process/task_queues:82:21) {
  errno: -2,
  code: 'ENOENT',
  syscall: 'spawn /bin/sh',
  path: '/bin/sh',
  spawnargs: [
    '-c',
    '/System/Library/Frameworks/CoreServices.framework/Versions/Current/Frameworks/LaunchServices.framework/Versions/Current/Support/lsregister -f -R -trusted -u MacOSATDriverServer.app'
  ],
  cmd: '/System/Library/Frameworks/CoreServices.framework/Versions/Current/Frameworks/LaunchServices.framework/Versions/Current/Support/lsregister -f -R -trusted -u MacOSATDriverServer.app',
  stdout: '',
  stderr: ''
}

Detect this specific error condition and provide a more detailed description, e.g.

Error: Cannot access directory: /Users/example/packages/macos-at-driver-server/MacOSATDriverServer/Build/Debug
    at exec (/Users/example/packages/macos-at-driver-server/shared/install/macos.js:42:13)
    at async unregisterExtensions (/Users/example/packages/macos-at-driver-server/shared/install/macos.js:195:3)
    at async exports.uninstall (/Users/example/packages/macos-at-driver-server/shared/install/macos.js:123:3)
    at async Object.handler (/Users/example/packages/macos-at-driver-server/shared/commands/uninstall.js:13:5) {
  [cause]: Error: spawn /bin/sh ENOENT
      at ChildProcess._handle.onexit (node:internal/child_process:284:19)
      at onErrorNT (node:internal/child_process:477:16)
      at process.processTicksAndRejections (node:internal/process/task_queues:82:21) {
    errno: -2,
    code: 'ENOENT',
    syscall: 'spawn /bin/sh',
    path: '/bin/sh',
    spawnargs: [
      '-c',
      '/System/Library/Frameworks/CoreServices.framework/Versions/Current/Frameworks/LaunchServices.framework/Versions/Current/Support/lsregister -f -R -trusted -u MacOSATDriverServer.app'
    ],
    cmd: '/System/Library/Frameworks/CoreServices.framework/Versions/Current/Frameworks/LaunchServices.framework/Versions/Current/Support/lsregister -f -R -trusted -u MacOSATDriverServer.app',
    stdout: '',
    stderr: ''
  }
}

---

@ChrisC: This should clear up the issue that you and I (and @stalgiag before us) have observed.

[ChrisC]

Looks good, tho I'm not sure it entirely clears up the issue that Stalgia reported, since it's very likely that the uninstall command is still not working.

[jugglinmike]

Agreed. This patch only disambiguates an error.