duplicate path in $PATH #899

Minor nit. We blindly prepend /usr/local/bin onto the $PATH without looking to see if it's already there. This leads to duplication.

docker run --rm -it python:3.12-slim

Python 3.12.1 (main, Jan 11 2024, 10:03:43) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.environ['PATH']
'/usr/local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin'

Expected output: /usr/local/bin:/usr/local/sbin:/usr/sbin:/usr/bin:/sbin:/bin

Or possibly the original path is fine? Since /usr/local/sbin already occurs before /usr/bin and /bin.

This applies to all the base images in here. They all come with PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin for the root user.