Add a build on windows stage

Jenkinsfile

@@ -42,5 +42,29 @@ pipeline {
                 }
             }
         }
+
+        stage ("Build Windows") {
+            agent {
+                label 'windows'
+            }
+
+            steps {
+                script {
+                    bat 'flutter pub get'
+                    bat 'flutter build windows'
+
+                    dir ("build/windows/x64/runner/release") {
+                        bat 'tar -cvf ../../../../../windows.tgz .'
+                    }
+                }
+            }
+            post {
+                success {
+                    archiveArtifacts artifacts: "windows.tgz"
+
+                    cleanWs()
+                }
+            }
+        }
     }
 }