[clang-tools-extra] [clangd] [C++20] [Modules] Introduce initial support for C++20 Modules (PR #66462)

[Chuanqi Xu via cfe-commits]

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@@ -112,6 +114,9 @@ class ClangdServer {
     /// This throttler controls which preambles may be built at a given time.
     clangd::PreambleThrottler *PreambleThrottler = nullptr;
 
+    /// Enable experimental support for modules.
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ChuanqiXu9 wrote:

I add ModulesManager to `ClangdServer::Options` and removed this flag. But I still need a variable to pass the information from the command line. I add that to `ClangdLSPServer::Options`. Otherwise we have to refactor the command line system of clangd a little bit. They are all local to `ClangdMain.cpp` now. If we really want that, I suggest we should do that in a separat patch.

https://github.com/llvm/llvm-project/pull/66462