[clangd] Fix background index not triggering on windows due to case mismatch.

Summary:
This isn't a general fix to all paths where we assume case-sensitivity, it's
a minimally-invasive fix targeting the llvm 9 branch.

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

Tags: #clang

Differential Revision: https://reviews.llvm.org/D65320

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@367112 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed