qbs: Fix link warning

for targeting xp 64bit, it's should be 5.2 (5.02)

LINK : warning LNK4010: invalid subsystem version number 5.01;
default subsystem version assumed

Change-Id: I8683a70148208ff399c6dfe3bd299b6b81206e32
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
Reviewed-by: Jake Petroules <jake.petroules@petroules.com>