Use getAttrFromPath instead of getAttr to supported nested build paths

build/release.nix

@@ -11,11 +11,11 @@ let
 					];
 				};
 			in
-				nixpkgsWithOverlays.lib.getAttr path nixpkgsWithOverlays;
+				nixpkgsWithOverlays.lib.getAttrFromPath path nixpkgsWithOverlays;
 
 	fakeOverlay = (import ../default.nix) null null;
 	packages = builtins.attrNames fakeOverlay.morepkgs;
-	generateBuilder = packageName: buildPath "morepkgs.${packageName}";
+	generateBuilder = packageName: buildPath ["morepkgs" packageName];
 
 	generatePackagePair = packageName: {
 		name = packageName;