Add a superbuild level option to control smtk documentation build

projects/smtk.cmake

@@ -20,6 +20,13 @@ if (vtkonly_enabled OR paraview_enabled)
   set(smtk_enable_vtk ON)
 endif ()
 
+# A convenient option to control smtk documentation
+option(ENABLE_SMTK_DOCUMENTATION "Enable smtk documentation" ON)
+set (enable_smtk_doc always)
+if (NOT ENABLE_SMTK_DOCUMENTATION)
+  set (enable_smtk_doc never)
+endif()
+
 if (UNIX AND NOT APPLE)
   list(APPEND smtk_extra_cmake_args
     -DCMAKE_INSTALL_RPATH_USE_LINK_PATH:BOOL=FALSE)
@@ -49,7 +56,7 @@ superbuild_add_project(smtk
   CMAKE_ARGS
     ${smtk_extra_cmake_args}
     -DBUILD_SHARED_LIBS:BOOL=ON
-    -DSMTK_BUILD_DOCUMENTATION:STRING=always
+    -DSMTK_BUILD_DOCUMENTATION:STRING=${enable_smtk_doc}
     -DSMTK_ENABLE_OPENCV:BOOL=${opencv_enabled}
     -DSMTK_ENABLE_QT_SUPPORT:BOOL=${qt_enabled}
     -DSMTK_ENABLE_VTK_SUPPORT:BOOL=${smtk_enable_vtk}