Switch the onder-riscv64 builder to Debian, enable dtrace

[furkanonder]

Since @StanFromIreland moved RISC-V to tier 3 in #791 we've got four riscv64 builders, and they were all Ubuntu.
I switched my board to Debian to increase distro diversity across the fleet.
While I was there I turned on --with-dtrace, which no other riscv64 worker has.

[StanFromIreland]

We might have to include it in d74e3cb, I'm not sure if the tests will pass on older branches?

[furkanonder]

We might have to include it in d74e3cb, I'm not sure if the tests will pass on older branches?

I tested it on the board. I built main with --with-dtrace and test_dtrace passes.

I don't think we need the d74e3cb skip. We only pass --with-dtrace on a PR or on 3.15+ (workers.py:76), so on 3.11 through 3.14 the worker builds without it and the < (3, 13) condition never applies.

[StanFromIreland]

LGTM

I'm not sure if you can merge here (?), if you can't send me a message on Discord when you're ready and I'm happy to land this.

[vstinner]

Good. The buildbot worker is green on 3.13, 3.14, 3.15 and main branches: https://buildbot.python.org/#/workers/104. It wasn't tested on 3.11 and 3.12 branches yet.