Handle riscv-arch-test as a git submodule

[stnolting]

Handle riscv-arch-test as a git submodule

[stnolting]

The current setup of the RISC-V architecture tests is some kind of leftover from the time where I was porting riscv-arch-test to verify the RISC-V compliance of the CPU. Including this as a submodule seems to be good idea. 👍

[umarcor]

riscv-arch-test was added as a submodule in a9f80b2. Hence, I'm closing this issue.

@stnolting you might want to add a dependabot configuration file such as https://github.com/im-tomu/fomu-workshop/blob/master/.github/dependabot.yml. That will check the upstream of the submodule periodically (you set the interval) and it will open PRs for having it updated.