Fix WITH_DOC

CMakeLists.txt

@@ -674,6 +674,7 @@ foreach (txt ${docs})
   string (REGEX REPLACE ".*/(.*)\\.txt" "\\1.html" html ${txt})
   set (src ${txt})
   set (dst doc/${html})
+  if (WITH_DOC)
     add_custom_command (
       OUTPUT  ${dst}
       COMMAND ${ASCIIDOC_EXECUTABLE}
@@ -686,7 +687,6 @@ foreach (txt ${docs})
       DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/${src}
       WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
       COMMENT "Generating ${html}")
-  if (WITH_DOC)
     list (APPEND html-docs ${CMAKE_CURRENT_BINARY_DIR}/${dst})
   endif ()
 endforeach ()