v12 - OpenCore for Catalina and Big Sur on Proxmox

I've updated the cpuid_set_cpufamily patch to fix a panic on boot on Big Sur 11.3 for AMD CPUs, and Intel CPUs that don't support AVX2.

This patch is in config.plist, so be sure to merge those changes if you're updating from an earlier version!

Diff in changes of config.plist since v11.