[clang-tools-extra] [clangd][test] Add `clang` to `CLANGD_TEST_DEPS`. (PR #230061)

[Aleksandr Platonov via cfe-commits]

https://github.com/ArcsinX approved this pull request.

This PR fixes for me problem which was rised [here ](https://github.com/llvm/llvm-project/pull/193426#issuecomment-6077040518).

The possible concern is that now we need to build clang executable to run clangd tests, so clean `check-clangd` build time will be significantly increased

https://github.com/llvm/llvm-project/pull/230061