Make llvm-link behave a bit more like LTO.

* Read modules lazily
* Don't treat the first file specially, instead merge all inputs into an empty
  module.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220501 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed