[clang-tools-extra] [clangd][modules] Remove the options that is for gcc, make modules work for clangd when using gcc (PR #200001)

[Aleksandr Platonov via cfe-commits]

ArcsinX wrote:

> Sorry for that, I think the database has already addressed with mangler in https://github.com/llvm/llvm-project/blob/main/clang-tools-extra/clangd/ClangdLSPServer.cpp#L566-L567, so I just want to ask why we need mangler again in this place.

`getProjectModules()` accepts `tooling::CompilationDatabase` which has no mangler inside `getCompileCommand()` call, but `ModulesBuilder` accepts `GlobalCompilationDatabase` (clangd internal implementation) and mangler is applied here automatically at `getCompileCommand()` call

https://github.com/llvm/llvm-project/pull/200001