This version of Linker.cpp works a lot better, but it's a little messy. Sorry.

This version of Linker.cpp works a lot better, but it's a little messy.  Sorry.

Use FileOpenable() instead of FileExists().
Create IsBytecode() predicate -- like IsArchive(), but for bytecode files.
Use IsBytecode() before trying to load any file as a bytecode file.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@9893 91177308-0d34-0410-b5e6-96231b3b80d8