zsh as Shell supported by GitLab Runner
Description
With macOS Catalina,macOS has officially switched from bash to zsh as the default shell. macOS GitLab CI runners are a common use-case for building iOS and macOS apps. Currently, users must workaround issues like translating shell profiles from zsh to bash in order to use shell runners on macOS. The version of bash shipped with macOS is known to be significantly out of date and marked as deprecated. Maintaining a user-installed copy of bash can be problematic, especially when the system is expecting to use the embedded, outdated copy. Adding official support for zsh will also provide for testing to ensure future updates to gitlab-runner operate as expected with zsh. -->
Proposal
Add official support for zsh as a gitlab-runner shell
Links to related issues and merge requests / references
Shells supported by GitLab Runner
Related issues: #27257 (closed) #1958 (closed)