Yeah, well, like I said -- use the calibre-git package from the AUR.
I actually maintain two AUR packages for calibre.
One is the binary i686/x86_64 installer from the calibre website, as used by my custom check-for-updates script and triggered by a systemd daemon. See
calibre-installer
The other is
calibre-git, which builds calibre from source.
Source builds are compiled by the Pi, which means it's for armv6 as well.
Do you use the AUR a lot? Official Arch policy is to only specify architectures that are supported by Arch Linux itself, and only i686/x86_64 are officially supported. That is why most PKGBUILDs don't include armv* in the arch=() array, even if they are known to work.
Standard Operating Policy on ArchLinuxARM is to build all packages using the "-A|--ignorearch" flag to makepkg (makechrootpkg does this automatically). Most of the time it will work.