...which represents the version of the MSVC platform toolset.
This variable is used to set the platform toolset version in .vcxproj
files. Before, the platform toolset version was determined in qmake's
C++ code. Now, it's set next to where MSVC_VER is set in common mkspecs
.conf files. This will simplify supporting new Visual Studio versions
in the future.
Change-Id: If78c921f93c6378829746d617c7e7d312174257e
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>