epstool: fix darwin build

pkgs/tools/graphics/epstool/default.nix

@@ -9,6 +9,12 @@ stdenv.mkDerivation rec {
     sha256 = "1pfgqbipwk36clhma2k365jkpvyy75ahswn8jczzys382jalpwgk";
   };
 
+  makeFlags = [
+    "CC=${stdenv.cc.targetPrefix}cc"
+    "CLINK=${stdenv.cc.targetPrefix}cc"
+    "LINK=${stdenv.cc.targetPrefix}cc"
+  ];
+
   installPhase = ''
     make EPSTOOL_ROOT=$out install
   '';
@@ -20,6 +26,6 @@ stdenv.mkDerivation rec {
     homepage = "http://pages.cs.wisc.edu/~ghost/gsview/epstool.htm";
     license = licenses.gpl2;
     maintainers = [ maintainers.asppsa ];
-    platforms = platforms.linux;
+    platforms = platforms.all;
   };
 }