Jenkins: Upload the kolibri APK after built

Add a parameter UPLOAD_APK to determine uploading the built Kolibri
Android packages, or not. It chains up kolibri-installer-android-upload
job.

https://phabricator.endlessm.com/T34805

Jenkinsfile

@@ -8,6 +8,14 @@ pipeline {
         }
     }
 
+    parameters {
+        boolean(
+            name: 'UPLOAD_APK',
+            default: false,
+            description: 'Upload the built Kolibri Android packages for internal testers'
+        )
+    }
+
     environment {
         // URL for the Kolibri wheel to include.
         // FIXME: It would be nice to cache this somehow.
@@ -78,6 +86,19 @@ pipeline {
                 }
             }
         }
+
+        stage('Upload APK') {
+            upload_apk = params.getOrDefault('UPLOAD_APK', false).toBoolean()
+            if (upload_apk) {
+                echo "Upload the built Kolibri Android packages for internal testers"
+                build(
+                    job: 'kolibri-installer-android-upload',
+                    parameters: [
+                        string(name: 'RELEASE_NOTES', value: '[]')
+                    ]
+                )
+            }
+        }
     }
 
     post {