jenkins: Disable building doxygen help in libosmocore

Change-Id: Iec6ad62c01aaaa7300086d130cc5512683f6c565
diff --git a/contrib/jenkins.sh b/contrib/jenkins.sh
index 4aa644c..679df6a 100755
--- a/contrib/jenkins.sh
+++ b/contrib/jenkins.sh
@@ -9,7 +9,7 @@
 
 cd libosmocore
 autoreconf --install --force
-./configure --prefix=$PWD/../install
+./configure --prefix=$PWD/../install ac_cv_path_DOXYGEN=false
 $MAKE $PARALLEL_MAKE install
 
 cd ../