set -e in fb_compile_mongo.sh

Summary: Based on @anthony's feedback, we want to fail early if our static linking fails.

Test Plan: none

Reviewers: anthony

Reviewed By: anthony

Subscribers: dhruba, anthony, leveldb

Differential Revision: https://reviews.facebook.net/D40839

build_tools/fb_compile_mongo.sh

 #!/bin/sh
 
+# fail early
+set -e
+
 if test -z $ROCKSDB_PATH; then
   ROCKSDB_PATH=~/rocksdb
 fi