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

#!/bin/sh

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

export CPATH=${CPATH}${CPATH:+':'}$(buildcpath ${NIX_CFLAGS_COMPILE})
export CPATH=${CPATH}${CPATH:+':'}@libc_includes@
export CPLUS_INCLUDE_PATH=${CPATH}${CPATH:+':'}@libcpp_includes@

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