get `arch` builds working again, because they are not

[joshrabinowitz]

See https://github.com/sobolevn/git-secret/runs/7564903813?check_suite_focus=true

Ends with:

checking keyring...
downloading required keys...
:: Import PGP key 139B09DA5BF0D338, "David Runge <[email protected]>"? [Y/n] 
checking package integrity...
:: File /var/cache/pacman/pkg/libcap-2.65-1-x86_64.pkg.tar.zst is corrupted (invalid or corrupted package (PGP signature)).
Do you want to delete it? [Y/n] error: libcap: signature from "David Runge <[email protected]>" is marginal trust
error: failed to commit transaction (invalid or corrupted package)

Errors occurred, no packages were upgraded.
The command '/bin/sh -c pacman -Syu --needed --noconfirm   bash   gawk   git   gnupg   diffutils   file   make   procps' returned a non-zero code: 1
make: *** [Makefile:52: docker-ci] Error 1
Error: Process completed with exit code 2.

[joshrabinowitz]

how popular are the arch packages? DO we want to maintain this?