ci: block release build while repo.multiflexi.eu is rebuilding

Add buildBlocker property so Jenkins holds the build in queue until
the ♻️ repo.mutiflexi.eu APT index rebuild finishes. This ensures
every build always installs the latest published .deb dependencies.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Vitexus

debian/Jenkinsfile.release

@@ -7,7 +7,13 @@ String imagePrefix = 'multiflexi-'
 //String distroFamily = ''
 
 properties([
-    copyArtifactPermission('*')
+    copyArtifactPermission('*'),
+    buildBlocker(
+        useBuildBlocker: true,
+        blockLevel: 'GLOBAL',
+        scanQueueFor: 'ALL',
+        blockingJobs: '.*repo.mutiflexi.eu'
+    )
 ])
 node() {
     ansiColor('xterm') {