[CMake] Circular dependencies because of file names?

[Jookia]

I have the following code:

# ---------- DOXYGEN

find_package(Doxygen)

set(docsDir "${CMAKE_BINARY_DIR}/docs/")

add_custom_command(OUTPUT ${docsDir}
   COMMAND ${CMAKE_COMMAND} "-E" "make_directory"
   ${docsDir} VERBATIM)

add_custom_target("docs"
   COMMAND "${DOXYGEN_EXECUTABLE}"
   "${CMAKE_SOURCE_DIR}/../doxygen/doxyfile"
   WORKING_DIRECTORY ${docsDir}
   DEPENDS ${docsDir})

set_directory_properties(PROPERTIES ADDITIONAL_MAKE_CLEAN_FILES
   "${docsDir}")

Which causes a circular conflict. But when I change the docsDir to 
"${CMAKE_BINARY_DIR}/docs2/", I no longer get the error.

Is there a way to fix this?