[Bug]: Entrypoint crashes on Void Linux if host uses Fish shell (package name mismatch)

Describe the bug When creating a Void Linux container on a host machine that uses the Fish shell, distrobox-init crashes due to a package name mismatch.

This happens because Distrobox attempts to install the host's shell using the package name fish. In the Void Linux xbps repository, the package is actually named fish-shell. The installation fails, but at the end of the init script, Distrobox still asserts command -v fish. This returns 127, causing a fatal error and preventing the /.containersetupdone file from being written.

Because the setup is never marked as "done", the container gets stuck in a crash loop on subsequent attempts to start and enter it.

To Reproduce

1. Host OS uses the fish shell as the default user shell.
2. Container OS: Void Linux (ghcr.io/void-linux/void-glibc-full:latest or musl).
3. Distrobox version: 1.8.2.5
4. Podman version: 5.8.2
5. Create the container: distrobox create -n void_test -i ghcr.io/void-linux/void-glibc-full:latest
6. Enter the container: distrobox enter void_test
7. The first entry attempt runs the init script, which fails to install fish.
8. Stop the container.
9. Try to start and enter the container again. It will permanently throw an "Error: An error occurred" and lock the user out because the setup script continually fails at the command -v fish check.

Expected behavior Distrobox should ideally have an xbps package exception that maps the host shell fish to the package fish-shell for Void Linux. Alternatively, if a custom host shell fails to install, the entrypoint should gracefully fallback to /bin/bash instead of crashing entirely on the command -v check.

Logs Here is the scrubbed trace showing the failure. First, xbps fails to find fish:

+ xbps-install -Syu xbps
[*] Updating repository `[https://repo-default.voidlinux.org/current/x86_64-repodata](https://repo-default.voidlinux.org/current/x86_64-repodata)' ...
Package 'xbps' is up to date.
+ xbps-install -Sy fish
ERROR: Package 'fish' not found in repository pool.

The script successfully falls back to installing bash and other base packages. However, at the very end of the entrypoint, it crashes here:

+ [ ! -e /.containersetupdone ]
+ command -v fish
+ SHELL=
+ [ 127 -ne 0 ]
+ printf 'Error: An error occurred\n'
Error: An error occurred

Desktop 
Host OS Opensuse Tumbleweed  
podman 5.8.2
Distrobox 1.8.2.5