Add common NixOS environment for all of the subprojects

default.nix

@@ -0,0 +1,13 @@
+with import <nixpkgs> {}; {
+    multikProtoEnv = stdenv.mkDerivation {
+        name = "multik-proto-env";
+        buildInputs = [ stdenv
+                        gcc
+                        pkgconfig
+                        cairo
+                        SDL2
+                        ffmpeg-full
+                        mlton
+                      ];
+    };
+}