contrib: Enable -Werror by default

Change-Id: I065b18dd6c4f7616f981aa4273e68e23825a7294
diff --git a/contrib/jenkins.sh b/contrib/jenkins.sh
index 88eda80..769d5a7 100755
--- a/contrib/jenkins.sh
+++ b/contrib/jenkins.sh
@@ -32,7 +32,7 @@
 set -x
 
 autoreconf --install --force
-./configure --enable-sanitize
+./configure --enable-sanitize CFLAGS="-Werror" CPPFLAGS="-Werror"
 $MAKE $PARALLEL_MAKE
 $MAKE distcheck \
   || cat-testlogs.sh