jenkins-build-srslte: Temporarily Switch git repo to own-controlled one

During integration of the different srsLTE processes, some bugs or
misbehaviors appear which require fixes in srsLTE. Let's use our own
temporary fork until integration is complete and all patches are merged
in upstream.

Change-Id: I6414d9855cf9c004385cc280e5a60e82f8e4fbad
diff --git a/contrib/jenkins-build-srslte.sh b/contrib/jenkins-build-srslte.sh
index 258354d..77d5bc4 100755
--- a/contrib/jenkins-build-srslte.sh
+++ b/contrib/jenkins-build-srslte.sh
@@ -3,7 +3,7 @@
 
 base="$PWD"
 name="srslte"
-git_url="https://github.com/srsLTE/"
+git_url="${git_url-"https://github.com/pespin/"}"
 . "$(dirname "$0")/jenkins-build-common.sh"
 
 #TODO: make sure libconfig, zeroMQ is installed