patches/openwrt: toolchain/gcc: reintroduce gcc 8.x
Reverts gcc 8.x removal from OpenWrt while leaving gcc 10 dropped.
This is needed to build TOS for Turris 1.x with PPC SPE instruction set extension enabled as these instructions are not supported since gcc 9.
HBD build still fails on applying packages patches afterwards, but this is unrelated.
Edited by Simon Borek