Clang Code Model on Ubuntu 19.10 fails to use /usr/include & /usr/include/x86_64-linux-gnu

The Clang Code Model in Qt Creator fails to find the "/usr/include" and "/usr/include/x86_64-linux-gnu" include paths with the GCC/G++ version currently in Ubuntu 19.10, as far as I can tell. (I assume it applies to the version as-shipped, but I haven't checked.)

(Those includes for which Clang has a replacement (such as stdint.h) started working between Qt Creator 4.10.0 and Qt Creator 4.11.0.)

In this situation, projects that attempt to include headers in these paths will find phantom errors appear from the Clang Code Model regarding missing include files.

An example would be "#include <pthread.h>".

(As such, an example project has not been included; take a library project template and add that into a header.)