nix: remove some unneeded dependencies, polishing

default.nix

@@ -2,7 +2,6 @@
   lib,
   beam_nox,
   fetchFromGitHub,
-  git,
   cmake,
   nixosTests,
   src,
@@ -11,7 +10,7 @@
 }:
 
 let
-  inherit (beam_nox.packages.erlang) mixRelease buildMix;
+  inherit (beam_nox.packages.erlang) mixRelease buildMix elixir;
 in
 mixRelease rec {
   pname = "mobilizon";
@@ -22,15 +21,6 @@ mixRelease rec {
 
   inherit src;
 
-  # See https://github.com/whitfin/cachex/issues/205
-  # This circumvents a startup error for now
-  stripDebug = false;
-
-  nativeBuildInputs = [
-    git
-    cmake
-  ];
-
   # Update deps.nix by running `mix deps.nix`
   mixNixDeps = import ./deps.nix {
     inherit lib;
@@ -60,9 +50,8 @@ mixRelease rec {
     );
   };
 
-  preConfigure = ''
-    export LANG=C.UTF-8 # fix elixir locale warning
-  '';
+  # fix elixir locale warning
+  env.LANG = "C.UTF-8";
 
   # Install the compiled js part
   preBuild = ''
@@ -84,7 +73,7 @@ mixRelease rec {
       ln -s ${ex_cldr.src}/priv/cldr/locales $out/lib/ex_cldr-${ex_cldr.version}/priv/cldr/locales
     '';
 
-  passthru.elixirPackage = beam_nox.packages.erlang.elixir;
+  passthru.elixirPackage = elixir;
 
   meta = with lib; {
     description = "Mobilizon is an online tool to help manage your events, your profiles and your groups";