rPackages.bigmemory: fix evaluation on darwin

On Darwin pkgs.libuuid is null, hence evaluating `.dev` fails.

pkgs/development/r-modules/default.nix

@@ -511,7 +511,7 @@ let
     nat = [ pkgs.which ];
     nat_templatebrains = [ pkgs.which ];
     pbdZMQ = lib.optionals stdenv.isDarwin [ pkgs.darwin.binutils ];
-    bigmemory = [ pkgs.libuuid.dev ];
+    bigmemory = lib.optionals stdenv.isLinux [ pkgs.libuuid.dev ];
     clustermq = [  pkgs.pkg-config ];
     RMark = [ pkgs.which ];
     RPushbullet = [ pkgs.which ];