Add USER env var to ensure the build can chown.

Change-Id: Ide58b9b5197d0f6534c3bb8bc2bd31c2b8523bd7
diff --git a/cicd/pipelines/enterprise/image_unstable.jenkins b/cicd/pipelines/enterprise/image_unstable.jenkins
index f6607d1..3d37596 100644
--- a/cicd/pipelines/enterprise/image_unstable.jenkins
+++ b/cicd/pipelines/enterprise/image_unstable.jenkins
@@ -24,7 +24,8 @@
             container('debian') {
                 def envVars = [
                     'IS_JENKINS=true',
-                    'RELEASE_NAME=unstable'
+                    'RELEASE_NAME=unstable',
+                    'USER=root'
                 ]
 
                 withEnv(envVars) {