[devsetup] install ocamlformat in "make devsetup"

Summary:
Now that we use stock ocamlformat we can install it as part of `make devsetup`
to set up a working dev environment.

Reviewed By: geralt-encore

Differential Revision:
D58725980

Privacy Context Container: L1258973

fbshipit-source-id: 76c553a0fdd8ba545412607ec178eb35ee064b9f

Makefile

@@ -967,7 +967,6 @@ endif
 .PHONY: devsetup
 devsetup:
 	$(QUIET)[ $(OPAM) != "no" ] || (echo 'No `opam` found, aborting setup.' >&2; exit 1)
-ifeq ($(OPAM_PIN_OCAMLFORMAT),yes)
 	$(QUIET)$(call silent_on_success,pinning ocamlformat,\
 	  OPAMSWITCH=$(OPAMSWITCH); \
 	  $(OPAM) pin add $$(cat "$(ABSOLUTE_ROOT_DIR)"/opam/ocamlformat) --yes --no-action)
@@ -977,7 +976,6 @@ ifeq ($(OPAM_PIN_OCAMLFORMAT),yes)
 	$(QUIET)$(call silent_on_success,installing ocamlformat,\
 	  OPAMSWITCH=$(OPAMSWITCH); \
 	  $(OPAM) install ocamlformat --yes)
-endif
 	$(QUIET)$(call silent_on_success,installing $(OPAM_DEV_DEPS),\
 	  OPAMSWITCH=$(OPAMSWITCH); $(OPAM) install --yes --no-depexts user-setup $(OPAM_DEV_DEPS))
 	$(QUIET)if [ "$(PLATFORM)" = "Darwin" ] && [ x"$(GNU_SED)" = x"no" ]; then \

Makefile.autoconf.in

@@ -82,7 +82,6 @@ OCAMLOPT := @OCAMLOPT@
 OPAM := @OPAM@
 OPAMROOT := @OPAMROOT@
 OPAMSWITCH := @OPAMSWITCH@
-OPAM_PIN_OCAMLFORMAT := @OPAM_PIN_OCAMLFORMAT@
 OTOOL := @OTOOL@
 PATCHELF := @PATCHELF@
 PATH := @PATH@

configure.ac

@@ -41,14 +41,6 @@ AC_CHECK_FILE([.git], [is_git_repo=yes], [is_git_repo=no])
 IS_GIT_REPO=$is_git_repo
 AC_SUBST([IS_GIT_REPO])
 
-AC_ARG_ENABLE(opam-pin-ocamlformat,
-  AS_HELP_STRING([--disable-opam-pin-ocamlformat],
-    [do not pin ocamlformat to the right version using opam and use the already-installed ocamlformat instead]),
-  ,
-  enable_opam_pin_ocamlformat=yes,)
-OPAM_PIN_OCAMLFORMAT=$enable_opam_pin_ocamlformat
-AC_SUBST([OPAM_PIN_OCAMLFORMAT])
-
 AC_ARG_VAR([PATH], [the shell's $PATH list of directories to search for executables])
 
 # to compile the facebook-clang-plugins