Upgrade to GCC v12.1

[mithro]

GCC v12.1 was recently released -- see https://lwn.net/Articles/894149/ -- The release notes say;

the RISC-V backend gained support for many new ISA extensions.

As we use a lot of RISC-V it seems like this would be an important release to upgrade to ASAP.

[mithro]

@PiotrZierhoffer - Is it possible to assign someone to make this happen?

[mithro]

Just FYI - https://groups.google.com/a/groups.riscv.org/g/sw-dev/c/aE1ZeHHCYf4