When ObjectFileMachO::GetModuleSpecifications is getting the ArchSpec
out of a binary, if the Mach-O binary is MH_PRELOAD ("standalone"), don't
let the OS be set to "ios" or "macosx" - there will be no dynamic loader
used when debugging this process.
<rdar://problem/9956443> 


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@189305 91177308-0d34-0410-b5e6-96231b3b80d8