[Qt-creator] QtCreator ignores scopes in .pro files

[Christoph Mathys]

Which parts of qmake-files does QtCreator consider? Some libraries
inside our project are optional, the .pro-file has clauses like this:

exists(libOptional/libOptional.pro) {
    SUBDIRS += libOptional
}

This is perfectly fine with qmake, but QtCreator complains regularly:
Could not find .pro file for sub dir 'libOptional' in '$<PROJECTDIR>'

This alone is a minor annoyance, but I suspect that this leads
QtCreator to reparse the entire source tree if I hit Ctrl+B. Is there
a way to include optional stuff that will allow QtCreator to "get it"?

Christoph