[PATCH] archlinux-keyring: harcode using bash as make's shell

Dear archlinux-keyring maintainers, Please find attached a patch to make the latest archlinux-keyring release (20220831) build on Debian/Ubuntu, where the default shell is Dash (and the build environment enforces this by passing SHELL=dash). Makefile seems to have acquired some Bash-isms ({} expansion) in 0831 that was not in 0727, and since the usage makes sense, hardcoding the shell to be bash would allow this to work without having to override Debian and Ubuntu builds for the affected targets. Thanks, -- Michel Alexandre Salim identities: https://keyoxide.org/5dce2e7e9c3b1cffd335c1d78b229d2f7ccc04f2