Kewlio: I'll see you guys next time

My latest dumb RPi project is trying to make it boot from a LUKS-encrypted partition. However, I have not succeeded in making this happen. The boot sequence does not ask for a passphrase, throws me into a busybox which does contain cryptsetup, but it doesn't let me actually open the encrypted volume because libgcc_s.so.1 is missing. I basically tried to follow this guide, making substitutions as needed from this other guide for booting from Btrfs (which that part by itself works), but no dice. :/