Make dynamic LLVMC plugins work on Windows (finally!).

Implemented by making lib/CompilerDriver a shared library that holds all the
global static data (CommandLine options, plugin registry) that we unfortunately
have to live with.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@74417 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed