[Qt-creator] CONFIG variables not as expected

[Bob Babcock]

I'm using Qt 5.14.0 and the bundled Creator 4.11.0 under Windows 7.
In a new or previously existing project using qmake, I display the contents 
of CONFIG by message($$CONFIG) in the .pro file.

For a msvc3015 project, I see win32-msvc2015 in the list values.

For a msvc2017 project, I do not see win32-msvc2017 or anything similar.

For a gcc project, I do not see debug_and_release like I do with msvc 
projects.

I can add
CONFIG *= debug_and_release
so I get debug and release build subdirectories, but detecting the compiler 
version is more awkward.