XCode projects don't build correctly after changing .ui files with Designer

When having an XCode project containing .ui files and changing these files in Designer and then saving the changes XCode does not correctly compile the changed project.

When pressing "Build" or "Build and Go" in XCode's project window XCode should generate .h files from .ui files and recompile all cpp files which include the changed .h file, instead only the .h files get created. Running the built app does not reflect the changes made to the .ui files. It is necessary to press "Build" twice before getting an up to date executable.