`make-pkg.sh` fails when `cp` from GNU utils is used

[noyannus]

Homebrew users often have the GNU utils masking the Mac's original BSD utils, e.g. cp invokes /usr/local/opt/coreutils/libexec/gnubin/cp.

This causes make-pkg.sh to fail because of the cp -X option.

As the users who need an Ext filesystem are more likely to also be GNU util users, consider adapting make-pkg.sh for both groups.

if [ $(which cp) == /usr/local/opt/coreutils/libexec/gnubin/cp ]; then 
  sed -i 's/cp -pRX /cp -pR /' ./fuse-ext2/tools/macosx/make-pkg.sh 
fi