Build libjpeg on MacOS

Take the steps below to avoid:

./libtool: unknown option character `-' in: --mode=compile

and

./libtool: Command not found

Those steps being:

tar -xzf jpegsrc.v6b.tar.gz
cd jpeg-6b/
ln -s /usr/bin/libtool ./libtool
cp /usr/share/libtool/config.sub .
cp /usr/share/libtool/config.guess .
./configure --enable-shared --enable-static
make
sudo make install