[sledge] Add fmt_all target to reformat no matter what dune thinks

Summary:
Dune does not track the ocamlformat binary as a dependency of the
`fmt` rules, so when testing or upgrading ocamlformat, the existing
`fmt` target is not reliable.

Reviewed By: jvillard

Differential Revision: D21441539

fbshipit-source-id: 40bea4447

sledge/Makefile

@@ -71,6 +71,13 @@ fmt:
 	clang-format -i model/llair_intrinsics.h model/cxxabi.cpp
 	${MAKE} -C test fmt
 
+OCAMLFORMAT_EXE = ocamlformat
+OCAMLFORMAT_ARGS =
+
+.PHONY: fmt_all
+fmt_all:
+	parallel $(OCAMLFORMAT_EXE) $(OCAMLFORMAT_ARGS) -i ::: $(shell find * \( -name _build -or -name llvm \) -not -prune -or \( -name '*'.ml -or -name '*'.mli \) -print 2>/dev/null)
+
 # print any variable for Makefile debugging
 print-%:
 	@printf '$*='; printf '$($*)'; printf '\n'