[clang-tools-extra] [clangd] [Modules] Support Reusable Modules Builder (PR #106683)

[Chuanqi Xu via cfe-commits]

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@@ -85,19 +85,20 @@ class PrerequisiteModules {
 /// different versions and different source files.
 class ModulesBuilder {
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ChuanqiXu9 wrote:

I didn't do it since in the last review, I was told we don't like forward declaration in clangd. And if we can do that, I like the style too.

https://github.com/llvm/llvm-project/pull/106683