[clang-tools-extra] [clangd] Support .clangd command line modifications for C++ modules (PR #122606)

[Chuanqi Xu via cfe-commits]

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@@ -9,6 +9,7 @@
 
 /// FIXME: Skip testing on windows temporarily due to the different escaping
 /// code mode.
+#include "llvm/ADT/StringRef.h"
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ChuanqiXu9 wrote:

Move the include after the `#ifndef`

https://github.com/llvm/llvm-project/pull/122606