Provisioning: Add Squish provisioning for Release Test Automation

Squish is required by RTA for testing.

Task-number: QTQAINFRA-1523
Change-Id: I0c3653565f19cc9b798a0b63325c47b017cf5537
Reviewed-by: Joni Jäntti <joni.jantti@qt.io>
Reviewed-by: Matti Paaso <matti.paaso@qt.io>

coin/provisioning/common/windows/helpers.ps1

@@ -127,3 +127,19 @@ function is64bitWinHost
         return 0
     }
 }
+
+Function Execute-Command
+{
+    Param (
+       [string]$command
+    )
+    Try {
+        echo "Executing command '$command'..."
+        $process = Start-Process -FilePath "cmd" -ArgumentList "/c $command" -PassThru -Wait -WindowStyle Hidden
+        if ($process.ExitCode) {throw "Error running command: '$command'"}
+    }
+    Catch {
+        $_.Exception.Message
+        exit 1
+    }
+}