Add support to get the shared cache information from the new

debugserver jGetSharedCacheInfo packet instead of reading 
the dyld internal data structures directly.  This code is 
(currently) only used for ios native lldb's - I should really
move this ObjectFileMachO::GetProcessSharedCacheUUID method
somewhere else, it makes less and less sense being in the
file reader.

<rdar://problem/25251243> 

llvm-svn: 276369