unscii: fix Darwin build

pkgs/data/fonts/unscii/default.nix

@@ -2,6 +2,11 @@
 , fontforge, SDL, SDL_image, mkfontscale
 }:
 
+let
+  perlenv = perl.withPackages (p: with p; [
+    TextCharWidth
+  ]);
+in
 stdenv.mkDerivation rec {
   pname = "unscii";
   version = "1.1";
@@ -12,11 +17,23 @@ stdenv.mkDerivation rec {
   };
 
   nativeBuildInputs =
-    [ (perl.withPackages (p: [ p.TextCharWidth ]))
+    [ perlenv
       bdftopcf fontforge SDL SDL_image
       mkfontscale
     ];
 
+  # Fixes shebang -> wrapper problem on Darwin
+  postPatch = ''
+    for perltool in *.pl; do
+      substituteInPlace Makefile \
+        --replace "./$perltool" "${perlenv}/bin/perl ./$perltool"
+    done
+  '';
+
+  makeFlags = [
+    "CC=${stdenv.cc.targetPrefix}cc"
+  ];
+
   preConfigure = ''
     patchShebangs .
   '';