sdbus: add build-sdbus.yml for riscv64 wheels - #1503

• Package: sdbus
• Version: 0.14.3
• Source: https://github.com/python-sdbus/python-sdbus/
• Docs: https://github.com/python-sdbus/python-sdbus

C extension binding libsystemd's sd-bus D-Bus API. Upstream publishes only a cp39 wheel, no riscv64.

Mirrors upstream's ci.yml unlimited/limited-API build and unittest steps.

Differs from upstream

• Links libsystemd dynamically via the image's systemd-devel, not upstream's from-source static build - manylinux_2_39_riscv64 already ships a modern libsystemd.
• abi3 floor is cp312 (RISE's min), not upstream's cp39 - setup.py never fixes the floor itself, so it's ours to pick.
• Dropped musllinux - libsystemd has no Alpine build; upstream tests Alpine against elogind instead.

Matrix: cp312-abi3 (built once, reused on cp313/cp314) + cp314t.

Testing

• same as upstream (unittest discover over test/, using its own private-bus fixture); added jinja2, matching upstream's own CI dependency for the interface-generator tests.

License: Wheel bundles libsystemd (LGPL-2.1-or-later) and libcap (BSD-3-Clause OR GPL-2.0-only); upstream ships no licence text for them, so the build adds it.

Built cp312 locally in the riscv64 manylinux container; wheel installs and the compiled extension loads correctly.