[hack] Add a toggle for Hacklang in build-infer.sh
[hack] Add a toggle for Hacklang in build-infer.sh

Summary: Adds an option to enable/disable as part of build-infer.sh script.

Reviewed By: ngorogiannis

Differential Revision: D38078373

fbshipit-source-id: 0866c2388522cfd8c84b1fb8e3c31a973c3f34f7

facebook/infer,facebook/infer,facebook/infer,facebook/infer,facebook/infer,facebook/infer,facebook/infer