[sledge] Add watch-test build target
[sledge] Add watch-test build target

Summary: To continuously build debug executables and run tests.

Reviewed By: peterogithub

Differential Revision: D31129957

fbshipit-source-id: 7fe23fd8b

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