[clang] [clang] Merge gtest binaries into AllClangUnitTests (PR #134196)

[Tom Honermann via cfe-commits]

tahonermann wrote:

I ended up spending a lot of time barking down the wrong rabbit hole due to these changes. @rnk, please see https://github.com/llvm/llvm-project/issues/140799.

https://github.com/llvm/llvm-project/pull/134196