Make sure we don't over specify an architecture when we connect to KDP and use...

Make sure we don't over specify an architecture when we connect to KDP and use the CPU type and subtype to fill out an architecture. We do this by letting the vendor be an unspecified unknown, or any. We also grab the target architecture, get the KDP host arch, and then merge the two before putting it back into the target.

Also change MH_PRELOAD to be use "unspecified unknown" (any) for the OS and vendor since these mach files can really be anything.

llvm-svn: 251579