[clang-tools-extra] [clangd] Re-land "support outgoing calls in call hierarchy" (PR #117673)

[Nathan Ridge via cfe-commits]

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@@ -163,7 +163,7 @@ class Checker {
   unsigned ErrCount = 0;
 
   Checker(llvm::StringRef File, const ClangdLSPServer::Options &Opts)
-      : File(File), Opts(Opts) {}
+      : File(File), Opts(Opts), Index(/*SupportContainedRefs=*/false) {}
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HighCommander4 wrote:

My original thinking was that `--check` does not perform any outgoing calls requests. But thinking more about it, a common use of `--check` is to reproduce crashes, so the more codepaths it executes (including the one behind this flag) the better in that regard.

https://github.com/llvm/llvm-project/pull/117673