ocamlPackages: fix some packages for cross-compilation

pkgs/development/ocaml-modules/afl-persistent/default.nix

@@ -12,7 +12,7 @@ stdenv.mkDerivation rec {
     sha256 = "06yyds2vcwlfr2nd3gvyrazlijjcrd1abnvkfpkaadgwdw3qam1i";
   };
 
-  buildInputs = [ ocaml findlib ];
+  nativeBuildInputs = [ ocaml findlib ];
 
   # don't run tests in buildPhase
   # don't overwrite test binary

pkgs/development/ocaml-modules/lwt/default.nix

@@ -17,8 +17,8 @@ buildDunePackage rec {
     sha256 = "0cq2qy23sa1a5zk6nja3c652mp29i84yfrkcwks6i8sdqwli36jy";
   };
 
-  nativeBuildInputs = [ pkg-config ];
-  buildInputs = [ cppo dune-configurator ]
+  nativeBuildInputs = [ pkg-config cppo dune-configurator ];
+  buildInputs = [ ]
    ++ optional (!versionAtLeast ocaml.version "4.08") ocaml-syntax-shims
    ++ optional (!versionAtLeast ocaml.version "4.07") ncurses;
   propagatedBuildInputs = [ libev mmap ocplib-endian seq result ];

pkgs/development/ocaml-modules/ocplib-endian/default.nix

@@ -11,7 +11,7 @@ buildDunePackage rec {
 
   useDune2 = true;
 
-  buildInputs = [ cppo ];
+  nativeBuildInputs = [ cppo ];
 
   meta = with lib; {
     description = "Optimised functions to read and write int16/32/64";