contrib/jenkins.sh: Allow jenkins job to specify if kernel GTP is used

Change-Id: I83319aa6e5e7dde229ae5a036b5a1800879cbf81
diff --git a/contrib/jenkins.sh b/contrib/jenkins.sh
index b2f8452..6a718a8 100755
--- a/contrib/jenkins.sh
+++ b/contrib/jenkins.sh
@@ -35,7 +35,7 @@
 
 cd "$base"
 autoreconf --install --force
-./configure
+./configure $GTP
 $MAKE $PARALLEL_MAKE
 $MAKE distcheck