[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:

After https://github.com/llvm/llvm-project/pull/201419 was landed, I don't see any problems if we remove unsupported options via `.clangd` config.

I doubt that it makes sense that every unsupported option should be described in the source code in order to be dropped. I see two options here:
- use the config, then everything already works
- automatically drop any unsupported command line argument.

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