Try running the Emacs container as root

Jenkinsfile

@@ -1,5 +1,10 @@
 pipeline {
-    agent { dockerfile true }
+    agent {
+        docker {
+            image 'silex/emacs:27.1-alpine-dev'
+            args '-u root --privileged'
+        }
+    }
 
     stages {
         stage('Build') {