python312Packages.itk: unbreak (#385166)

pkgs/top-level/python-packages.nix

···
     inherit python numpy;
     enablePython = true;
     enableRtk = false;
+    stdenv = if stdenv.cc.isGNU then pkgs.stdenvAdapters.useLibsFrom stdenv pkgs.gcc12Stdenv else stdenv;
   });