Broken linking of non-Qt libs in Qmake-generated vcxproj files

PROBLEM:

• Linker error to 'libEGLd.lib' when building a Qt3d project. (details in attached file).
• Linking to custom libraries specified with "LIBS +=" in .pro files is also broken in vcxproj-files generated by qmake.
• This is a regression compared to Qt 5.6 alpha.

CAUSE:

• $$(QTDIR)\lib is not properly added to "Additional linker directories" any more.
• Suspect that this is related to the recent rewrite of windows library handling in qtbase https://codereview.qt-project.org/#/c/126371/ merging of MingwMakefileGenerator::findLibraries() into Win32MakefileGenerator https://codereview.qt-project.org/#/c/126373/.
• The reason for my suspicion is that parameters that should have been additional linker directories instead show up with a "-L" prefix in the list of libraries to link to. Visual Studio does not understand this prefix.