As zsh's corresponding flag is called --no-rcs, the build environment
couldn't be configured to use zsh at all.
Even then the custom PS1 won't work on zsh, but it's usable enough.
Close#1040.
This option allows the user to specify commands to run when the shell
exits. This can be used to cleanup operations done in `extraCmds'.
Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>
