[sledge] Reformat after promoting tests

Summary:
The result of promoting expect tests is not necessarily formatted, so
try to reduce iterations by formatting after testing.

Reviewed By: ngorogiannis

Differential Revision: D20004973

fbshipit-source-id: 53af4c034

sledge/Makefile

@@ -67,7 +67,8 @@ watch: setup
 
 .PHONY: test
 test: setup
-	dune build @_build/dbg/runtest --auto-promote
+	-dune build @_build/dbg/runtest --auto-promote
+	dune build $(FMTS) --auto-promote
 
 .PHONY: ci-test
 ci-test: setup