Use ZipFile.CreateFromDirectory for reliable subdirectory inclusion in zip

Jenkinsfile

@@ -41,7 +41,7 @@ pipeline {
 
         stage('Deploy to Azure') {
             steps {
-                bat 'powershell -Command "Compress-Archive -Path publish\\* -DestinationPath deploy.zip -Force"'
+                bat 'powershell -Command "Add-Type -Assembly System.IO.Compression.FileSystem; if (Test-Path deploy.zip) { Remove-Item deploy.zip }; [System.IO.Compression.ZipFile]::CreateFromDirectory(\'publish\', \'deploy.zip\')"'
                 withCredentials([azureServicePrincipal(
                     credentialsId:          'azure-pcl',
                     subscriptionIdVariable: 'AZ_SUB_ID',