Don't check MSVC_VERSION if not building for Windows.

Change-Id: Ia98209f8ec98772a9c7328a9bd181d6cd53f1b77
Small SConscript cleanup.

Change-Id: Id33eb147f78bdaa31876fadb9df0aa89022e84ba
Fix WinRT build.

Change-Id: Ic6934bced65342a30236e6f4ffa9265854898459