message: fix Miri script on macOS
diff: @@ -39,7 +39,11 @@ EOF
  TARGET=$(rustc --version --verbose | grep "^host:" | cut -d ' ' -f 2)
  SYSROOT=$(rustc --print sysroot)
  LIBDIR=$SYSROOT/lib/rustlib/$TARGET/lib
  -MIRIDIR=$(readlink -e "$(dirname "$0")")
  +MIRIDIR=$(dirname "$0")
  +if readlink -e . >/dev/null; then
  + # This platform supports `readlink -e`.
  + MIRIDIR=$(readlink -e "$MIRIDIR")
  +fi
  if ! test -d "$LIBDIR"; then
  echo "Something went wrong determining the library dir."
  echo "I got $LIBDIR but that does not exist."
  