[clang-tools-extra] [wip][clangd] Introduce --skip-preamble-build command line option (PR #189284)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

> > Headers should belong to the global module fragments. This is by design. Attaching headers to module purview may be warned: https://godbolt.org/z/3rTM19r9P
> 
> But here we have no warnings https://godbolt.org/z/xPeohsMEf

This is just some implementation choices. By design, the original legacy headers should be in GMF for sure. 

https://github.com/llvm/llvm-project/pull/189284