Pass -g option when compiling ppx extensions.

https://github.com/ocaml/dune/pull/3671

3671.patch

@@ -0,0 +1,38 @@
+From a176b0ce6d6be0cdd6c7b04c3d655cae567527e2 Mon Sep 17 00:00:00 2001
+From: Rudi Grinberg <me@rgrinberg.com>
+Date: Tue, 4 Aug 2020 00:56:34 -0700
+Subject: [PATCH] Pass -g when compiling ppx preprocessor
+
+Signed-off-by: Rudi Grinberg <me@rgrinberg.com>
+---
+ CHANGES.md                | 2 ++
+ src/dune/preprocessing.ml | 3 ++-
+ 2 files changed, 4 insertions(+), 1 deletion(-)
+
+diff --git a/CHANGES.md b/CHANGES.md
+index 3bb8c04160..f195d7ca45 100644
+--- a/CHANGES.md
++++ b/CHANGES.md
+@@ -76,6 +76,8 @@ next
+ - Fix a stack overflow when displaying large outputs (including diffs) (#3537,
+   fixes #2767, #3490, @emillon)
+ 
++- Pass `-g` when compiling ppx preprocessors (#3671, @rgrinberg)
++
+ 2.6.0 (05/06/2020)
+ ------------------
+ 
+diff --git a/src/dune/preprocessing.ml b/src/dune/preprocessing.ml
+index 87c765256c..53a391448b 100644
+--- a/src/dune/preprocessing.ml
++++ b/src/dune/preprocessing.ml
+@@ -332,7 +332,8 @@ let build_ppx_driver sctx ~dep_kind ~target ~pps ~pp_names =
+         (Build.record_lib_deps
+            (Lib_deps.info ~kind:dep_kind (Lib_deps.of_pps pp_names)))
+     >>> Command.run compiler ~dir:(Path.build ctx.build_dir)
+-          [ A "-o"
++          [ A "-g"
++          ; A "-o"
+           ; Target target
+           ; A "-w"
+           ; A "-24"

ocaml-dune.spec

@@ -6,7 +6,7 @@
 
 Name:           ocaml-%{libname}
 Version:        2.6.2
-Release:        1%{?dist}
+Release:        2%{?dist}
 Summary:        A composable build system for OCaml
 
 # Dune itself is MIT.  Some bundled libraries have a different license:
@@ -22,6 +22,10 @@ License:        MIT and LGPLv2 and LGPLv2 with exceptions and ISC
 URL:            https://dune.build
 Source0:        https://github.com/ocaml/%{libname}/archive/%{version}/%{libname}-%{version}.tar.gz
 
+# Pass -g when compiling ppx extensions.
+# https://github.com/ocaml/dune/pull/3671
+Patch1:         3671.patch
+
 BuildRequires:  emacs
 BuildRequires:  ocaml >= 4.07
 BuildRequires:  ocaml-findlib
@@ -191,6 +195,10 @@ cp -ar README.md CHANGES.md MIGRATION.md doc/_build/* %{buildroot}%{_pkgdocdir}/
 %{_emacs_sitelispdir}/dune*
 
 %changelog
+* Tue Aug  4 2020 Richard W.M. Jones <rjones@redhat.com> - 2.6.2-2
+- Pass -g option when compiling ppx extensions.
+  https://github.com/ocaml/dune/pull/3671
+
 * Mon Aug  3 2020 Jerry James <loganjerry@gmail.com> - 2.6.2-1
 - New version 2.6.2