[clang] [clang-tools-extra] [clang-format] Fix leaking of host-level config into test environment (PR #206358)

[Damian Höster via cfe-commits]

damster101 wrote:

> I don't see any harm on the clang-format file.

Well, I used an out-of-source build directory (should have mentioned that), so the .clang-format affecting those tests was not the one in the root dir of the llvm project, but my personal one in my home directory.

https://github.com/llvm/llvm-project/pull/206358