python312Packages.libvirt: fix cross build

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

@@ -1,4 +1,5 @@
 {
+  stdenv,
   lib,
   buildPythonPackage,
   fetchFromGitLab,
@@ -21,6 +22,11 @@ buildPythonPackage rec {
     hash = "sha256-zOjTGXwxjd6QT01AaIln0FdP/8UZS0W3yPltUhlocpk=";
   };
 
+  postPatch = ''
+    substituteInPlace setup.py \
+      --replace-fail 'pkg-config' "${stdenv.cc.targetPrefix}pkg-config"
+  '';
+
   build-system = [ setuptools ];
 
   nativeBuildInputs = [ pkg-config ];