Stop installing the ocaml-syntax-shims binary (#2654)

Signed-off-by: Jeremie Dimino <jeremie@dimino.org>

CHANGES.md

@@ -130,6 +130,10 @@
   the executable source. Programs that use this feature can be run by a new
   action (dynamic-run <progn> ...). (#2635, @staronj, @aalekseyev)
 
+- Stop installing the `ocaml-syntax-shims` binary. In order to use
+  `future_syntax`, one now need to depend on the `ocaml-syntax-shims`
+  package (#2654, @diml)
+
 - Add support for dependencies that are re-exported. Such dependencies
   are marked with`re_export` and will automatically be provided to
   users of a library (#2605, @rgrinberg)

doc/concepts.rst

@@ -448,6 +448,11 @@ compilers.
 One example of supported syntax is the custom let-syntax that was
 introduced in 4.08, allowing the user to define custom let operators.
 
+Note that this feature is implemented by the third-party
+`ocaml-syntax-shims project
+<https://github.com/ocaml-ppx/ocaml-syntax-shims>`, so if you use this
+feature you must also declare a dependency on this package.
+
 .. _deps-field:
 
 Dependency specification

dune

@@ -0,0 +1,6 @@
+;; We embed a copy of ocaml-syntax-shims until we drop support for
+;; OCaml < 4.08
+(env
+ (_
+  (binaries
+   (src/ocaml-syntax-shims/pp.exe as ocaml-syntax-shims))))

src/ocaml-syntax-shims/dune

@@ -1,7 +1,5 @@
 (executable
  (name pp)
- (package dune)
- (public_name ocaml-syntax-shims)
  (libraries compiler-libs.common))
 
 (ocamllex let_trail)