Provide gcc-9.3.0-r1 binpkg to match gentoo stable arm64

[lifers]

From Set Up Your RPi as a distcc Client

As we are using a stable-branch compiler on the PC, but the RPi image uses the 'testing' (aka ~arm64) branch by default, begin by downgrading your gcc compiler (and binutils, for consistency) on the RPi to the 'stable' version (this version is also available on the binhost, so the following process shouldn't take long). Issue:

Just checked your binhost, seems no binary matched this list, so my pi3 compiled and halted.

[sakaki-]

30 Oct 2020: sadly, due legal obligations arising from a recent change in my 'real world' job, I must announce I am standing down as maintainer of this project with immediate effect. For the meantime, I will leave the repo up (for historical interest, and since the images may be of use still in certain applications); however, there will be no further updates to the underlying binhost etc., nor will I be accepting / actioning further pull requests or bug reports from this point. Email requests for support will also have to be politely declined, so, please treat this as an effective EOL notice.

For further details, please see my post here.

Many thanks for your interest in this project!

With sincere apologies, sakaki ><