vtk: fix build with clang 16

pkgs/development/libraries/vtk/generic.nix

@@ -86,6 +86,10 @@ in stdenv.mkDerivation rec {
       "-DVTK_PYTHON_VERSION:STRING=${pythonMajor}"
     ];
 
+  env = lib.optionalAttrs stdenv.cc.isClang {
+    NIX_CFLAGS_COMPILE = "-Wno-error=incompatible-function-pointer-types";
+  };
+
   postPatch = optionalString stdenv.isDarwin ''
     sed -i 's|COMMAND vtkHashSource|COMMAND "DYLD_LIBRARY_PATH=''${VTK_BINARY_DIR}/lib" ''${VTK_BINARY_DIR}/bin/vtkHashSource-${majorVersion}|' ./Parallel/Core/CMakeLists.txt
     sed -i 's/fprintf(output, shift)/fprintf(output, "%s", shift)/' ./ThirdParty/libxml2/vtklibxml2/xmlschemas.c