[clang-tools-extra] [clangd] fix wrong resouce-dir (PR #203332)

[via cfe-commits]

playerC wrote:

> > In this case , the resource-dir generated from clangd , is pointed to a **directory not exists**
> 
> That's unexpected, and may indicate an issue with how clangd is installed.
> 
> Can you say more about how you installed clangd on your system? There may be a bug in the script that packaged it, in which case that bug should be addressed instead.

I am working on openbsd 7.9 , and on this system, clangd install prefix is `/usr/local` , and  user llvms install prefix is `/usr/local/llvmXX/`.

when using default pkg to install clang-tools-extra, it  will depend on a specific version of llvm and it will be installed automaticly, with the install prefix.  

And other version of llvm is also packaged with same install prefix, but different version number in that path.

I don't knonw how to set the install prefix is match the clangd 's requirement. 

Do you have any idea?  it should be package with `/usr/local` or `/usr/local/llvmXX`.

And great thanks for your help.

https://github.com/llvm/llvm-project/pull/203332