nixpkgs/pkgs/development/tools/clang-tools/wrapper

#!/bin/sh

buildcpath() {
  local path after
  while (( $# )); do
    case $1 in
        -isystem)
            shift
            path=$path${path:+':'}$1
            ;;
        -idirafter)
            shift
            after=$after${after:+':'}$1
            ;;
    esac
    shift
  done
  echo $path${after:+':'}$after
}

export CPATH=${CPATH}${CPATH:+':'}$(buildcpath ${NIX_CFLAGS_COMPILE} \
                                               $(<@clang@/nix-support/libc-cflags)):@clang@/resource-root/include
export CPLUS_INCLUDE_PATH=${CPLUS_INCLUDE_PATH}${CPLUS_INCLUDE_PATH:+':'}$(buildcpath ${NIX_CFLAGS_COMPILE} \
                                                                                      $(<@clang@/nix-support/libcxx-cxxflags) \
                                                                                      $(<@clang@/nix-support/libc-cflags)):@clang@/resource-root/include

exec -a "$0" @unwrapped@/bin/$(basename $0) "$@"