Jenkinsfile: Correctly set pipeline status on a build failure.

Otherwise the pipeline cannot be meaningfully used as a validation
job, as it'd always return success, even upon encountering one or more
build failures.

* Jenkinsfile: In case a packaging target failed building, set the
build result to failure.

Change-Id: I47c8b09936b088b27a02173aa94a0adb0f04dcb4

Jenkinsfile

@@ -134,7 +134,7 @@ See https://wiki.savoirfairelinux.com/wiki/Jenkins.jami.net#Configuration"
                                 node('linux-builder') {
                                     cleanWs()
                                     unstash 'release-tarball'
-                                    catchError(buildResult: 'SUCCESS',
+                                    catchError(buildResult: 'FAILURE',
                                                stageResult: 'FAILURE') {
                                         sh """
                                            tar xf *.tar.gz --strip-components=1