libjpeg: Define NO_GETENV for WinRT

getenv isn't available on this platform, and has been stripped from the
lib starting with MSVC2013.

Change-Id: I5a69055b7c3ca85dc6d5a74c5b2842e7886b13bd
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
qmake: add the store library path on WinRT

Starting with MSVC2013, a separate set of libs for Windows Store apps is
supplied, so make sure it is in the LIBPATH (and before the desktop libs).

Change-Id: I74f3f385c2db749010fbfe7e2d4c3d1228e4e603
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>