Summary:
AFAIK proper /bin/sh does not support "+=". Note that only our
changes use "+=". The Google code does A="$A + $B" rather than A+=$B.

Task ID: #

Blame Rev:

Test Plan:
build

Revert Plan:

Database Impact:

Memcache Impact:

Other Notes:

EImportant:

- begin *PUBLIC* platform impact section -
Bugzilla: #
- end platform impact -

Reviewers: dhruba

Reviewed By: dhruba

Differential Revision: https://reviews.facebook.net/D6231