contrib: add trigger

contrib/ci.inria.fr/Jenkinsfile-basic

@@ -6,6 +6,12 @@ pipeline
 {
 	agent none
 
+	// Trigger the build
+	triggers {
+		// Poll gitlab explicitly every 15mn
+		pollSCM('00-59/15 * * * *')
+	}
+
 	stages
 	{
 		stage('Tarball')