mkPythonMetaPackage: Create a top_level.txt file in build output

In NixOS#337621 I had initially
created an empty, but importable package, meaning that initial
tests worked just fine, because the top_level.txt file is always
created when an importable package exists.

Subsequent refactors removed the importable package, but didn't verify
that the dependency satisfaction still works, only that the
metadata output looked good.

It was a bit tricky to express what I wanted to with hatchling, so I switched to setuptools.

pkgs/development/interpreters/python/meta-package.nix

@@ -1,7 +1,7 @@
 {
   buildPythonPackage,
   lib,
-  hatchling,
+  setuptools,
 }:
 {
   pname,
@@ -16,6 +16,11 @@
 # This is useful for packages that have a split binary/source dichotomy like psycopg2/psycopg2-binary,
 # where we want to use the former, but some projects declare a dependency on the latter.
 
+let
+  pyname = lib.replaceStrings [ "-" ] [ "_" ] pname;
+
+in
+
 buildPythonPackage {
   inherit
     pname
@@ -45,14 +50,16 @@ buildPythonPackage {
       ))
     )}
 
-    [tool.hatch.build.targets.wheel]
-    bypass-selection = true
+    [tool.setuptools]
+    packages = [ "${pyname}" ]
 
     [build-system]
-    requires = ["hatchling"]
-    build-backend = "hatchling.build"
+    requires = ["setuptools"]
+    build-backend = "setuptools.build_meta"
     EOF
+
+    mkdir ${pyname}
   '';
 
-  build-system = [ hatchling ];
+  build-system = [ setuptools ];
 }