vtk: unbreak on OS X

pkgs/development/libraries/vtk/default.nix

@@ -57,7 +57,7 @@ stdenv.mkDerivation rec {
     ++ optional enablePython [ "-DVTK_WRAP_PYTHON:BOOL=ON" ];
 
   postPatch = stdenv.lib.optionalString stdenv.isDarwin ''
-    sed -i 's|COMMAND vtkHashSource|COMMAND "DYLD_LIBRARY_PATH=''${VTK_BINARY_DIR}/lib" ''${VTK_BINARY_DIR}/bin/vtkHashSource-7.0|' ./Parallel/Core/CMakeLists.txt
+    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
     sed -i 's/fprintf(output, shift)/fprintf(output, "%s", shift)/g' ./ThirdParty/libxml2/vtklibxml2/xpath.c
   '';

pkgs/top-level/all-packages.nix

@@ -14844,7 +14844,7 @@ in
   vte_290 = callPackage ../development/libraries/vte/2.90.nix { };
 
   vtk = callPackage ../development/libraries/vtk {
-    stdenv = gcc8Stdenv;
+    stdenv = if stdenv.isDarwin then stdenv else gcc8Stdenv;
     inherit (darwin) libobjc;
     inherit (darwin.apple_sdk.libs) xpc;
     inherit (darwin.apple_sdk.frameworks) Cocoa CoreServices DiskArbitration