Incorrect path to PowerShell.exe when mounting point for drive C isn't default in WSL 2

[kuzalekon]

The #217 PR broke ability to start ReactJS app in dev mode for me. When trying to start it using yarn start command I get an error:

events.js:292
      throw er; // Unhandled 'error' event
      ^

Error: spawn /mnt/c/Windows/System32/WindowsPowerShell/v1.0/powershell.exe ENOENT
    at Process.ChildProcess._handle.onexit (internal/child_process.js:269:19)
    at onErrorNT (internal/child_process.js:465:16)
    at processTicksAndRejections (internal/process/task_queues.js:80:21)

...

As we can see from message - powershell.exe not found. That happened because I'm didn't use default mounting point for drive C. My mounting point for C is different - /c instead of /mnt/c.
But the #217 PR change dynamically determination of mounting point to constant (see 53 line)
Mounting point should be determined dynamically as it be in v7.3.0.

[sindresorhus]

// @anaisbetts

[anaisbetts]

I'll see what I can do tomorrow

[kuzalekon]

@anaisbetts The #219 PR will fix this problem. Please review it. Thanks in advance!

[kuzalekon]

Fixed by #219 PR.