jenkins.sh: add --enable-werror to configure flags

Change-Id: If3af8d0fe9247c22d57dbe70fc80a58ee7297f75
diff --git a/contrib/jenkins.sh b/contrib/jenkins.sh
index 44152dc..222bd8f 100755
--- a/contrib/jenkins.sh
+++ b/contrib/jenkins.sh
@@ -37,7 +37,7 @@
 
 cd "$base"
 autoreconf --install --force
-./configure $MGCP --enable-vty-tests --enable-external-tests
+./configure $MGCP --enable-vty-tests --enable-external-tests --enable-werror
 $MAKE $PARALLEL_MAKE
 LD_LIBRARY_PATH="$inst/lib" $MAKE check \
   || cat-testlogs.sh