Get clangd to find standard headers in nix-shell

[gabyx]

I use the following as @tobim suggests:

Clangd issues on nixos: missing headers

Like so: # C++ # Clangd from clang-tools must come first. (hiPrio clang-tools.override { llvmPackages = llvmPackages_16; enableLibcxx = false; }) # Do not use the clangd from this package as it does not work correctly with # stdlib headers. llvmPackages_16.libstdcxxClang