Separate doxygen doc building from other docs

doc/CMakeLists.txt

@@ -2,18 +2,20 @@
 
 find_package(Doxygen)
 
-if(DOXYGEN_FOUND)
-    configure_file(${CMAKE_CURRENT_SOURCE_DIR}/Doxyfile.in ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile @ONLY)
+if(BUILD_DOXYGEN_DOC)
+    if(DOXYGEN_FOUND)
+        configure_file(${CMAKE_CURRENT_SOURCE_DIR}/Doxyfile.in ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile @ONLY)
 
-    add_custom_target(doc
-        COMMAND ${DOXYGEN_EXECUTABLE} ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile
-        WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
-        COMMENT "Generating API documentation with Doxygen"
-        VERBATIM)
+        add_custom_target(doc
+            COMMAND ${DOXYGEN_EXECUTABLE} ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile
+            WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
+            COMMENT "Generating API documentation with Doxygen"
+            VERBATIM)
 
-    install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/html DESTINATION ${CMAKE_INSTALL_DOCDIR} OPTIONAL)
-else()
-    message(WARNING "Documentation enabled, but Doxygen cannot be found")
+        install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/html DESTINATION ${CMAKE_INSTALL_DOCDIR} OPTIONAL)
+    else()
+        message(WARNING "Documentation enabled, but Doxygen cannot be found")
+    endif()
 endif()
 
 install(FILES sdbus-c++-class-diagram.png