Script doesn't play well with GNU coreutils installed in PATH

[1dolla]

When using GNU coreutils, either via MacPorts or Homebrew, and with these in path, createinstalliso has multiple fail points (mktemp and stat so far, as I'm trying to get it running), as it assumes the binaries in $PATH are the macOS bundles ones.

Fix: use absolute paths for macOS binaries, e.g. /usr/bin/mktemp and /usr/bin/stat, or simply alias them locally at the beginning of the script, like

alias stat=/usr/bin/stat
...

Cheers :)

[1dolla]

Also, it would be nice to be able to select your own temp folder, but that's unrelated.