There is an updated pull request by jnbr against master on the void-packages repository

https://github.com/jnbr/void-packages gcc
https://github.com/void-linux/void-packages/pull/12988

gcc: import upstream patch for bug 90756
This patch is necessary to build firefox 68 on i686.
Apparently only i686 and s390x are affected by this bug, so only patch the i686 cross tool chains.

A patch file from https://github.com/void-linux/void-packages/pull/12988.patch is attached