jenkins: add postbuildscript plugin

Signed-off-by: Milosz Wasilewski <milosz.wasilewski@linaro.org>
Change-Id: I9d699afa06efa408236d8225646c1b5697f86056
diff --git a/jessie-amd64-jenkins-master/plugins.txt b/jessie-amd64-jenkins-master/plugins.txt
index 44e191e..66b30f3 100644
--- a/jessie-amd64-jenkins-master/plugins.txt
+++ b/jessie-amd64-jenkins-master/plugins.txt
@@ -22,6 +22,7 @@
 multiple-scms:0.6
 parameterized-trigger:2.39
 pipeline-utility-steps:2.6.1
+postbuildscript:2.9.1
 rebuild:1.31
 ssh-agent:1.20
 ssh-slaves:1.31.2