Always run Ruby activation using cmd for RubyInstaller

[vinistock]

Motivation

Closes #2434

Our Ruby environment activation script doesn't work for Windows user who select their default shell as Powershell due to quote escaping issues.

I believe cmd.exe will always be available and it's the default option when invoking NodeJS' exec function, so instead of trying to escape the script differently depending on the shell, I think we should just always run RubyInstaller activation on cmd.exe.

Implementation

I created an override for runScript, which removes the shell part for RubyInstaller only.

Automated Tests

Added a test verifying that we're not passing shell to exec.