New issue by rn-gh on void-packages repository

https://github.com/void-linux/void-packages/issues/42673

Description:
I wanted to submit a patch for [`srcpkgs/gcc`](https://github.com/void-linux/void-packages/tree/master/srcpkgs/gcc) to enable GDC, the D language compiler (`--enable-languages=...,d`), and hit a wall (https://gcc.gnu.org/install/prerequisites.html):

> In order to build GDC, the D compiler, you need a working GDC compiler (GCC version 9.4 or later) and D runtime library, ‘libphobos’, as the D front end is written in D.
> 
> Versions of GDC prior to 12 can be built with an ISO C++11 compiler, which can then be installed and used to bootstrap newer versions of the D front end.

How can I make this work? Package (temporarily) gcc-11 + gcc-d-11 and build gcc + gcc-d with it?