[clangd] Handle windows line endings in QueryDriver

Summary: fixes second case of https://github.com/clangd/clangd/issues/93

Reviewers: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64789

llvm-svn: 366320