message: Fix extern build on Linux.
diff: #!/bin/sh
  ORIGINALDIR=$PWD
  -EXTERNDIR=$(dirname "$0")
  +SCRIPT=$(readlink -f "$0")
  +EXTERNDIR=$(dirname "$SCRIPT")
  +echo $EXTERNDIR
  cd $EXTERNDIR
  mkdir build
  cd build
  -
  # Draco
  cd $EXTERNDIR
  cd build
  -mkdir draco; cd draco
  +mkdir draco
  +cd draco
  cmake ../../draco/
  cmake --build . --config Release
  