Resolve the executable _before_ we try to get the module specifications.

Also fixed the host 32 and 64 bit arch to return "x86_64-apple-macosx" again instead of "x86_64-apple-" (unspecified OS) after recent changes.

<rdar://problem/17845078> 


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@214223 91177308-0d34-0410-b5e6-96231b3b80d8