As I am sure a lot of people already know, Zak Kemble distributes Windows and Linux binaries for avr-gcc with the latest released versions (GCC 9.1, Binutils 2.32), you can get his stuff here: http://blog.zakkemble.net/avr-gcc-builds/
The only problem is, it also ships avr-libc V2. Which is the latest release, but is in both dog years, and internet time, ANCIENT. There are patches to support the xmega3 devices, like : ATtiny212, ATtiny214, ATtiny412, ATtiny414, ATtiny416, ATtiny417, ATtiny814, ATtiny816, ATtiny817, ATtiny1614, ATtiny1616, ATtiny1617, ATtiny3214, ATtiny3216, ATtiny3217 for avr-libc but they have sat for a while, and given patches for that project are waiting on some action since 2006, I wouldn't hold any breath hoping there will be a avr-libc V2.1 that includes that support.
SO, i decided to rectify that. https://github.com/stevenj/avr-gcc-build-script is a modified version of Zaks script, which will build avr-libc from the latest SVN source, not the last release back in 2016. And applies the xmega3 patches. This creates a toolchain which has full xmega3 support without messing around copying files from "packs" or microchip archives, to coble together something approaching xmega3 support. It will still create windows and linux binaries, but i have only tested on linux.