>> BTW, is there any resource point to why the package of the
>> avr-toolchain 5.5 is broken?
>
> I searched through my mail and I don't remember exactly where I read
> that avr-toolchain 5.5 is broken and avr-toolchain 4.9 works.

I found the bug report I was looking for. Hope that helps!

https://issues.guix.info/issue/24416