[drone-runner-docker] powershell.exe hardcoded as shell

Running WCOW throws the following error:

Error response from daemon: container […] encountered an error during hcs::System::CreateProcess: failure in a Windows system call: The system cannot find the file specified. (0x2)

After some investigation, I found the cause of the error.
“powershell” is hardcoded in the script generator of the compiler github.
Unfortunately, windows containers based on nanoserver do not come with a ‘powershell.exe’ but with a ‘pwsh.exe’ instead.

refer to Windows docker pipeline use drone/git image?