Can't build with toolchain-atmelavr on darwin_arm64

Because every ARM Mac with Rosetta (2) installed should be capable of executing executing x64 binaries. The workings of this were confirmed 2 years ago in Platform IDE for VSCode on Mac ARM/M1? - #17 by ivankravets.

CC @ivankravets or @manuelbl can you check a simple Arduino Uno project on an ARM Mac?