install_name_tool: add expression

pkgs/os-specific/darwin/install_name_tool/default.nix

···
+{ stdenv }:
+
+assert stdenv.isDarwin;
+
+stdenv.mkDerivation {
+  name = "install_name_tool";
+  src = "/usr/bin/install_name_tool";
+  unpackPhase = "true";
+  configurePhase = "true";
+  buildPhase = "true";
+
+  installPhase = ''
+    mkdir -p "$out"/bin
+    ln -s "$src" "$out"/bin
+  '';
+
+  meta = with stdenv.lib; {
+    description = "Change dynamic shared library install names";
+    homepage    = https://developer.apple.com/library/mac/documentation/Darwin/Reference/Manpages/man1/install_name_tool.1.html;
+    maintainers = with maintainers; [ lovek323 ];
+    platforms   = platforms.darwin;
+
+    longDescription = ''
+      Install_name_tool changes the dynamic shared library install names and or
+      adds, changes or deletes the rpaths recorded in a Mach-O binary.
+    '';
+  };
+}
+

pkgs/top-level/all-packages.nix

···
 
   apg = callPackage ../tools/security/apg { };
 
+  install_name_tool = callPackage ../os-specific/darwin/install_name_tool { };
+
   xcodeenv = callPackage ../development/mobile/xcodeenv { };
 
   titaniumenv_2_1 = import ../development/mobile/titaniumenv {

pkgs/top-level/python-packages.nix

···
       sha256 = "1rvgrviwn6f037m8vq395chz6a1119dbsdhfwdbv5ambi0bak6ll";
     };
   
-    buildInputs = [ pkgs.libspotify ];
+    buildInputs = [ pkgs.libspotify ]
+      ++ stdenv.lib.optional stdenv.isDarwin pkgs.install_name_tool;
   
     # python zip complains about old timestamps
     preConfigure = ''