What's the current status? This bug is almost 3 years old and Debian is still shipping 5.4.0, even in Sid. nightwalker-87 mentions that Arch Linux may have found a working solution:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=932989#20
- Bug#932989: gcc-avr: Package version severely outdated compared... Marco
