buildbot: fix withPlugins

buildPythonPackage started failing if there was no setup.py, so disable the
build and check phases. Also, fix the package name so the python version isn't
duplicated.

pkgs/development/python-modules/buildbot/default.nix

···
 
 let
   withPlugins = plugins: buildPythonPackage {
-    name = "${package.name}-with-plugins";
+    pname = "${package.pname}-with-plugins";
+    inherit (package) version;
+
     dontUnpack = true;
+    dontBuild = true;
+    doCheck = false;
+
     nativeBuildInputs = [ makeWrapper ];
     propagatedBuildInputs = plugins ++ package.propagatedBuildInputs;