[clang-tools-extra] [clangd] Enable query-based custom checks (PR #216336)

[Peiqi Li via cfe-commits]

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@@ -69,6 +70,7 @@
 #include <cstddef>
 #include <iterator>
 #include <memory>
+#include <mutex>
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voyager-jhk wrote:

> We use `mutex` under `#if CLANG_TIDY_ENABLE_QUERY_BASED_CUSTOM_CHECKS`. Does unconditional `#include <mutex>` rise an unused include warning if `CLANG_TIDY_ENABLE_QUERY_BASED_CUSTOM_CHECKS` is not set?
> 
> The same question for newly added `#include "../clang-tidy/ClangTidy.h"`

Moved both includes under the feature guard. Thanks.

https://github.com/llvm/llvm-project/pull/216336