Shorten Slicer build path
Shorten Slicer build path

This creates problems on windows due to the limitations of cl.exe memory.
There are simply too many characters in the many include directories that
each target has.
To reduce the number of characters, we can shorten the build directory of
slicer.

KitwareMedical/VesselView,matthieuheitz/VesselView,KitwareMedical/VesselView,agirault/VesselView,sumedhasingla/VesselView,agirault/VesselView,agirault/VesselView,matthieuheitz/VesselView,sumedhasingla/VesselView,matthieuheitz/VesselView,KitwareMedical/VesselView,sumedhasingla/VesselView