nixpkgs/pkgs/misc/vim-plugins/vim2nix/additional-nix-code/clang_complete

    # In addition to the arguments you pass to your compiler, you also need to
    # specify the path of the C++ std header (if you are using C++).
    # These usually implicitly set by cc-wrapper around clang (pkgs/build-support/cc-wrapper).
    # The linked ruby code shows generates the required '.clang_complete' for cmake based projects
    # https://gist.github.com/Mic92/135e83803ed29162817fce4098dec144
    # as an alternative you can execute the following command:
    # $ eval echo $(nix-instantiate --eval --expr 'with (import <nixpkgs>) {}; clang.default_cxx_stdlib_compile')
    preFixup = ''
      substituteInPlace "$out"/share/vim-plugins/clang_complete/plugin/clang_complete.vim \
        --replace "let g:clang_library_path = '' + "''" + ''" "let g:clang_library_path='${llvmPackages.clang.cc}/lib/libclang.so'"
    '';