watchman: remove use of asprintf from the watch command
watchman: remove use of asprintf from the watch command

Summary: as above

Reviewed By: chadaustin

Differential Revision: D17783431

fbshipit-source-id: fee50ff6bc831367f0fe73fb46b734c55c6f1eb7

facebook/watchman,facebook/watchman,facebook/watchman,facebook/watchman,nodakai/watchman,nodakai/watchman,facebook/watchman,facebook/watchman,facebook/watchman,nodakai/watchman,nodakai/watchman,nodakai/watchman,nodakai/watchman,nodakai/watchman,nodakai/watchman,nodakai/watchman,facebook/watchman,facebook/watchman