Nix build: Use newer avr-gcc, add x86_64 binary.
Nix build: Use newer avr-gcc, add x86_64 binary.

fixator/aprinter,fixator/aprinter,ambrop72/aprinter,fixator/aprinter,johnkingsley/aprinter,johnkingsley/aprinter,ambrop72/aprinter,ambrop72/aprinter,fixator/aprinter,ambrop72/aprinter,ambrop72/aprinter,johnkingsley/aprinter,johnkingsley/aprinter,fixator/aprinter,johnkingsley/aprinter,johnkingsley/aprinter,ambrop72/aprinter,fixator/aprinter,ambrop72/aprinter,johnkingsley/aprinter