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

[Nathan Ridge via cfe-commits]

HighCommander4 wrote:

Sorry, I misunderstood what was meant by the "discovered clang binary" in the issue description. I thought it was referring to the compiler used to build the code (from the compile command, or [this `Compiler` config option](https://clangd.llvm.org/config#compiler)), but I now see that you're actually adding a new config option to customize the path used to determine the resource dir.

Instead of adding a new config option, would clangd's [existing `-resource-dir` command-line option](https://searchfox.org/llvm/rev/8f069e7aea7dbf35d87c8a7a700ae6871b831298/clang-tools-extra/clangd/tool/ClangdMain.cpp#129-135) work for your use case?

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