New comment by alekseyt on void-packages repository

https://github.com/void-linux/void-packages/pull/16891#issuecomment-601951004

Comment:
I've updated PR for GCC 9.3.0, some changes overlap with master, but nothing should conflict, i've also rebased it on newer master.

Other changes:
* MPFR is synced with `gcc/template` (4.0.2)
* added tar to `hastmakedepends` - this was already added in master, now conflict with this branch is also resolved