A bit of a fix to handle frameworks better

The issue is neither VTK or CMake handle multi architecture framework builds very well. In the case of VTK system introspection is used and system introspection is sorf of iffy for cross compiling multiple architecures into one tree. This patch just breaks up the builds so that for ios devices each architecture is its own tree. There is still an issue in that only one header file gets used in a framework so we will eventually need to look at removing some of the system introspection from VTKs build and instead using header files with ifdefs in them.