Generalize building of Elixir interpreter

pkgs/development/beam-modules/default.nix

@@ -37,9 +37,16 @@ let
         buildMix = callPackage ./build-mix.nix {};
 
         # BEAM-based languages.
-        elixir = if versionAtLeast (lib.getVersion erlang) "18"
-                 then callPackage ../interpreters/elixir { debugInfo = true; }
-                 else throw "Elixir requires at least Erlang/OTP R18.";
+        elixir = defaultScope.elixir-1_4;
+
+        elixir-1_4 = if versionAtLeast (lib.getVersion erlang) "18"
+                     then lib.callElixir ../interpreters/elixir/1.4.nix { debugInfo = true; }
+                     else throw "Elixir requires at least Erlang/OTP R18.";
+
+        elixir-1_3 = if versionAtLeast (lib.getVersion erlang) "18"
+                     then lib.callElixir ../interpreters/elixir/1.3.nix { debugInfo = true; }
+                     else throw "Elixir requires at least Erlang/OTP R18.";
+
         lfe = callPackage ../interpreters/lfe { };
 
         # Non hex packages

pkgs/development/beam-modules/lib.nix

@@ -43,4 +43,12 @@ rec {
         mkDerivation = pkgs.makeOverridable builder;
       };
 
+  callElixir = drv: args:
+    let
+      builder = callPackage ../../development/interpreters/elixir/generic-builder.nix args;
+    in
+      callPackage drv {
+        mkDerivation = pkgs.makeOverridable builder;
+      };
+
 }