Fix IOS builds failing due to improperly configured vtk_glew.h

ThirdParty/glew/CMakeLists.txt

-if (VTK_OPENGL_USE_GLES OR ANDROID)
+if(VTK_OPENGL_USE_GLES OR ANDROID AND NOT VTK_IOS_BUILD)
   set(VTK_MODULE_vtkglew_GLES3 1)
 endif()
 
-if (NOT BUILD_SHARED_LIBS)
+if(NOT BUILD_SHARED_LIBS)
   set(GLEW_STATIC 1)
 endif()
 
 include(CMakeDependentOption)
-cmake_dependent_option(VTK_MODULE_vtkglew_IS_SHARED "Whether the glew in use is shared or not" ON
+cmake_dependent_option(VTK_MODULE_vtkglew_IS_SHARED
+  "Whether the glew in use is shared or not" ON
   VTK_USE_SYSTEM_GLEW "${BUILD_SHARED_LIBS}")
 mark_as_advanced(VTK_MODULE_vtkglew_IS_SHARED)
-if (VTK_MODULE_vtkglew_IS_SHARED)
+if(VTK_MODULE_vtkglew_IS_SHARED)
   set(VTK_SYSTEM_GLEW_SHARED 1)
-endif ()
+endif()
 
 vtk_module_third_party(GLEW)