In 16219a31db we implemented a post-up
hook that checked for a problematic `/etc/zshenv` file. OSX/macOS has
changed the file responsible for executing `path_helper` and loading the
system paths multiple times, and this script change issued a warning to
users if `path_helper` might be called in such a way that their paths
could be unexpectedly reordered.
The script used colored output to highlight this problem for the user,
and relied on Bash's script path introspection (through `$BASH_SOURCE`)
to print the location of the `post-up` hook to assist the user in
troubleshooting and understanding where our warning came from.
This change removes the hook's reliance on GNU Bash in favor of `sh`. It
uses the POSIX-compliant `$0` to determine the hook location (this
method is less robust than Bash's `$BASH_SOURCE`, but is available in
all POSIX shells) and removes colored output in the warning to be
compatible with shells that don't support colored output.
Fix#517.
06197218c7