The previous version rebound the `hash` and `rehash` builtins to
reassing GNU utils when they were called. This didn't take into
account that when `$PATH` changes, the commands are rehashed as
well.

This version adds a preexec hook to reassign the GNU utilities
before running any command, if and only if they aren't already
reassigned. This is checked by looking at the `whoami` command.

Fixes #10535

Co-authored-by: Robert Lankford <robert.lankford@nuorder.com>

GNU "make" is installed as "gmake" by homebrew.

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>