gn build: Unbreak Windows build

I didn't break all that much during upstreaming, just needs two small fixes:

- fix spelling of MCJITTests.def file
- make libLTO a shared_library to put it in bin/ on Windows where it is in the
  CMake build too

Differential Revision: https://reviews.llvm.org/D56630


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351004 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed