Adding a path to the PATH environment variable in the current PowerShell session is simpler than I thought:
> $env:path += ";path"
Note: remember to prepend the semi-colon to the new path make a valid path list.
You can make your PATH variable persistent using the
SetEnvironmentVariable() .Net method:
[System.Environment]::SetEnvironmentVariable("PATH", $Env:Path + ";path", "target")
… where target is "Machine", "User" or "Process". Check the .Net documentation for what these values mean.