cmake: move utility macros to a separate module

CMake/vtkDirectories.cmake

-macro (vtk_set_with_default var value)
-  if (NOT ${var})
-    set(${var} "${value}")
-  endif ()
-endmacro ()
-
 # VTK installation structure
 set(vtk_subdir "vtk-${VTK_MAJOR_VERSION}.${VTK_MINOR_VERSION}")
 vtk_set_with_default(VTK_INSTALL_RUNTIME_DIR "bin")

CMake/vtkSupportMacros.cmake

+macro (vtk_set_with_default var value)
+  if (NOT ${var})
+    set(${var} "${value}")
+  endif ()
+endmacro ()

CMakeLists.txt

@@ -18,6 +18,7 @@ include(vtkInitializeBuildType)
 include(vtkVersion)
 set(VTK_VERSION
     "${VTK_MAJOR_VERSION}.${VTK_MINOR_VERSION}.${VTK_BUILD_VERSION}")
+include(vtkSupportMacros)
 include(vtkDownload)
 include(vtkTesting)
 include(vtkDirectories)