[Interest] QMAKESPEC and Qt 5.9

[Philippe]

In the past I used to specify QMAKESPEC. For example,

set QMAKESPEC=winrt-x64-msvc2015

However, since 5.9.1, the Qt configure complains:

"Please make sure to unset the QMAKESPEC,..."

When I remove set QMAKESPEC, the build is fine...

However, the config.summary file lists "win32-msvc" and not
"winrt-x64-msvc2015"

How can I make sure the proper mkspecs is used?...

Philippe