New issue by Anachron on void-packages repository

https://github.com/void-linux/void-packages/issues/45239

Description:
### Is this a new report?

Yes

### System Info

Void 6.3.10_1 x86_64 GenuineIntel uptodate rrFFFFFFF

### Package(s) Affected

xbps-src

### Does a report exist for this bug with the project's home (upstream) and/or another distro?

No.

### Expected behaviour

I expect `LANG=C ./xbps-src update-check bsdtar` to throw no errors on bash.

### Actual behaviour

```bash
# LANG=C ./xbps-src update-check bsdtar
/home/lap/var/bldr/gitsrc/common/environment/setup/sourcepkg.sh: line 31: unset: `BASH_FUNC_filew%%': not a valid identifier
/home/lap/var/bldr/gitsrc/common/environment/setup/sourcepkg.sh: line 31: unset: `BASH_FUNC_timer_handle%%': not a valid identifier
/home/lap/var/bldr/gitsrc/common/environment/setup/sourcepkg.sh: line 31: unset: `BASH_FUNC_welcome_prompt_handle%%': not a valid identifier
/home/lap/var/bldr/gitsrc/common/environment/setup/sourcepkg.sh: line 31: unset: `BASH_FUNC_vimw%%': not a valid identifier
/home/lap/var/bldr/gitsrc/common/environment/setup/sourcepkg.sh: line 31: unset: `BASH_FUNC_directory_not_found_handle%%': not a valid identifier
/home/lap/var/bldr/gitsrc/common/environment/setup/sourcepkg.sh: line 31: unset: `BASH_FUNC_shell_prompt_handle%%': not a valid identifier
/home/lap/var/bldr/gitsrc/common/environment/setup/sourcepkg.sh: line 31: unset: `BASH_FUNC_gitw%%': not a valid identifier
/home/lap/var/bldr/gitsrc/common/environment/setup/sourcepkg.sh: line 31: unset: `BASH_FUNC_cdw%%': not a valid identifier
/home/lap/var/bldr/gitsrc/common/environment/setup/sourcepkg.sh: line 31: unset: `BASH_FUNC_command_not_found_handle%%': not a valid identifier
libarchive-3.6.2 -> libarchive-3.7.0

```

### Steps to reproduce

Run `LANG=C ./xbps-src update-check bsdtar` with shell functions inside bashs env.

Issue is because of https://github.com/void-linux/void-packages/commit/6174bd6afde26fbcdf80437ab1653c6dab34099b

@sgn