Description:

In /etc/profile the function appendpath is used to add the default PATH entries.
This function is later unset with 'unset appendpath'.

The problem with this is, that it isn't POSIX compliant to assume, that this will actually unset the function. The relevant part of the POSIX standard reads:
(https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#unset)
> If neither -f nor -v is specified, name refers to a variable; if a variable by that name does not exist, it is unspecified whether a function by that name, if any, shall be unset.

Most shells just unset the function if the variable doesn't exist (bash, dash, ksh), but not zsh.
Therefor every zsh instance started as a login shell has a function appendpath in it's environment (if not unset in a later script).

Fix:
Fixing this is trivial. Just add the -f flag to 'unset appendpath'.
I have verified that this works for bash, dash, ksh and zsh.

Diff of /etc/profile:
19c19
< unset appendpath
---
> unset -f appendpath


Additional info:
* version of the filesystem package: 2019.10-2

Steps to reproduce:
In a shell run:
zsh -l
echo $PATH | grep test --color=always
appendpath test
echo $PATH | grep test --color=always
whence -v appendpath
exit