QtCreator 4.15.0 breaks conan/cmake

After updating to QtCreator 4.15, our CMake/Conan based build is broken (we use conan.cmake from within CMake to install conan requirements).

I' m not quite sure what's happening here exactly. But I see a conan-dependencies directory, see that our conan imports step was executed there (which alone takes 15 minutes) and that there is a `conan_paths.cmake` which is unusable/wrong for our use-case.

I tried to disable the preferences option "Package manager auto setup" and cleaned everything before retrying, but it didn't help. 

However, after emptying the conan_paths.cmake created by QtCreator, deleting the CMakeCache.txt and manually running conan install (with our settings) again, I was able to configure, build and link our project from within QtCreator again. But of course, this is not a reasonable solution.

Generally speaking, I do see that this can be a nice feature. But for projects like ours - with existing CMake/Conan files and support for Visual Studio, XCode, CLion and QtCreator, this automatic is also tricky. Therefore, shouldn't QtCreator just ask if it should do such things automatically?