Refactor(build-clan): rename to lib/modules

This is a preparation for moving everything into clan, to make it all one module evaluation

lib/modules/function-adapter.nix

@@ -0,0 +1,27 @@
+{
+  lib,
+  nixpkgs,
+  nix-darwin ? null,
+  clan-core,
+  self,
+  specialArgs ? { },
+}:
+# Returns a function that takes self, which should point to the directory of the flake
+module:
+(lib.evalModules {
+  specialArgs = {
+    inherit
+      self
+      clan-core
+      nixpkgs
+      nix-darwin
+      ;
+  };
+  modules = [
+    (lib.modules.importApply ./interface.nix { inherit (clan-core) clanLib; })
+    module
+    {
+      inherit specialArgs;
+    }
+  ];
+}).config