macOS is obnoxious and overwrites the PATH from a users ~/.zshenv, which is
sourced first, in /etc/zprofile by calling `/usr/libexec/path_helper -s` so
this is required so that PATH is once again set to the desired value.
Add ccache symlink directory to start of PATH, this must be after
`typeset -U PATH` because on macOS this reorders the list so ccache's
symlinks will no longer be at the start of PATH rendering it unusable.
