Script Fails on MacOSX under powershell core due to $env:TEMP

[65156]

Windows only variable has been referenced in Get-AzureRMCloudCapability.ps script breaking functionality with non Windows Operating systems.

Please consider using unified variable "[system.io.path]::GetTempPath()"

link here https://github.com/Azure/AzureStack-Tools/blob/master/CloudCapabilities/AzureRM.CloudCapabilities.psm1#L48

replace:
$rootPath = $env:TEMP
with:
$rootPath = [system.io.path]::GetTempPath()

would have issued a pull request myself to fix this but its greyed out?