turn off multi-pass RCC for Visual Studio projects

For multi-pass RCC qmake generates broken VS project files, because
the RCC extra compiler directly calls the C++ compiler on a generated
source file. Adding this call to a VS project file will bypass any
project settings. Also, the VS project generator is not prepared to
add extra compilers that generate object files.

Task-number: QTBUG-39685
Change-Id: I1bcaad8936be8371d596f29ed8952888ba95f7b2
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
don't compile the xcode generator on Windows

With MSVC it takes minutes to compile pbuilder_pbx.cpp.
So let's remove this generator that's never used.

Change-Id: I13038d551283d96dfb0baf0b8a8a68c6538193c8
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>