Build docs always if enabled

Author: OliverRietmann

docs/CMakeLists.txt

@@ -5,7 +5,7 @@ set(DOXYGEN_OUT ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile)
 
 configure_file(${DOXYGEN_IN} ${DOXYGEN_OUT} @ONLY)
 
-add_custom_target(docs
+add_custom_target(docs ALL
     COMMAND ${DOXYGEN_EXECUTABLE} ${DOXYGEN_OUT}
     WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
     COMMENT "Generating API documentation with Doxygen"