Verilator Actions fail due to missing RV GCC tool package

[calebofearth]

This Verilator run (https://github.com/chipsalliance/caliptra-rtl/actions/runs/7284166844/job/20212806445?pr=357) fails because it lost access to the 12.1.0 RV gcc toolchain we've been using.

See: remove old multilib toolchain · stnolting/riscv-gcc-prebuilt@f21324a (github.com).

We need a more stable image to compile code for Verilator Actions.

[mkurc-ant]

Hi. Sure, I'll look into that.