Fix that the list "cmd" was turned into a string if one of the proxy
vars was set in the environment. Add a test for this code path. Before
this patch:
$ FTP_PROXY=test pmbootstrap -v --details-to-stdout status
…
% cd /home/user/.local/var/pmbootstrap/cache_git/pmaports; git remote -v
run: FTP_PROXY=test ['git', 'remote', '-v']
ERROR: [Errno 2] No such file or directory: "FTP_PROXY=test ['git', 'remote', '-v']"
Fixes: 1a00c04f ("pmb.helpers.run_core: always configure proxy vars if set in environment")
Reviewed-by: Clayton Craft <clayton@craftyguy.net>
Link: https://lists.sr.ht/~postmarketos/pmbootstrap-devel/%3C20230713182337.6185-3-ollieparanoid@postmarketos.org%3E