Add RISC-V support

[Sakura286]

Add riscv64 trampoline. All tests in Criterion has passed. Here is the test log.

[MrAnno]

Wow! Thank you for this pull request.

[Snaipe]

Awesome!

I'd rather not leave this untested though. There's no riscv support on Alpine Linux to build a proper snaipe/ci-meson image with qemu-user as a foreign-arch binfmt interpreter, but maybe we can add a job to cross-compile the test binaries on riscv64, then use qemu-user-riscv64 to run them?

[Sakura286]

Yes, it should be tested.

I tried to cross-build to riscv64 in amd64 Debian/Ubuntu on Cirrus CI , Github Action , local Docker. The script does the same thing, but only test on Cirrus CI failed because of CoreDump (see script on my branch: Sakura286@e04455025). I haven't figured out why this happend till now.

Does this subject accept other CI if Cirrus is not usable?