use the same CFLAGS as ocaml would use

OBS-URL: https://build.opensuse.org/package/show/devel:languages:ocaml/ocaml-stdcompat?expand=0&rev=12

ocaml-stdcompat.spec

@@ -16,6 +16,7 @@
 #
 
 
+%global  _buildshell /bin/bash
 %define _lto_cflags %{nil}
 Name:           ocaml-stdcompat
 Version:        15
@@ -28,6 +29,7 @@ URL:            https://opam.ocaml.org/packages/stdcompat
 Source0:        %{name}-%{version}.tar.xz
 BuildRequires:  autoconf
 BuildRequires:  automake
+BuildRequires:  bash
 BuildRequires:  ocamlfind(findlib)
 BuildRequires:  ocaml-rpm-macros >= 20210409
 BuildRequires:  ocaml(ocaml.opt)
@@ -48,6 +50,10 @@ developing applications that use %{name}.
 %autosetup -p1
 
 %build
+values=( `ocamlc.opt -config-var native_c_compiler` )
+export CC="${values[0]}"
+unset values[0]
+export CFLAGS="${values[@]}"
 %make_build -f Makefile.bootstrap
 %configure \
 	--libdir=%{ocaml_standard_library}