Added message to inform that step may take a while

Change-Id: I8f609fb34a7c7c3db85cfaf06a810f290ac5a026
Reviewed-on: https://weave-review.googlesource.com/1072
Reviewed-by: Vitaly Buka <vitalybuka@google.com>
diff --git a/libweave/examples/ubuntu/prerequisites.sh b/libweave/examples/ubuntu/prerequisites.sh
index f2bc580..af9aeac 100755
--- a/libweave/examples/ubuntu/prerequisites.sh
+++ b/libweave/examples/ubuntu/prerequisites.sh
@@ -54,6 +54,7 @@
 ./autogen.sh || exit 1
 ./configure --disable-shared || exit 1
 make || exit 1
+echo -e "\n\nTesting libevent...\nCan take several minutes.\n"
 make verify || exit 1
 cp -rf include/* $ROOT_DIR/third_party/include/ || exit 1
 cp -rf .libs/lib* $ROOT_DIR/third_party/lib/ || exit 1