lightgbm riscv64 support

Package name (on PyPI)

lightgbm

Source repository

https://github.com/lightgbm-org/LightGBM

Version(s) requested

4.7.0

Why is this needed?

LightGBM is one of the two mainstream gradient-boosting libraries. Upstream publishes py3-none wheels for macOS, Windows, x86_64 and aarch64 Linux, but nothing for riscv64, so pip install lightgbm on riscv64 falls back to the sdist and needs a CMake/C++ toolchain.

Additional context

Workflow added in #481. The build and auditwheel repair succeed and the wheel carries a real lib_lightgbm.so, but the test phase segfaults in the ranking tests — see #617 for the underlying cause, which is not in LightGBM.

The wheel bundles Eigen, fast_double_parser, fmt and nanoarrow; upstream's license-files = ["LICENSE"] shipped none of their licence texts, so the port carries a patch adding them.

Beginne damit, den in #481 hinzugefügten Workflow und die LightGBM 4.7.0 Wheel-Build-Konfiguration zu lesen. Reproduziere den Build und die auditwheel-Reparatur und folge dann #617, um den Segfault im ranking-test zu verstehen. Als abgeschlossen gilt die Aufgabe, wenn ein riscv64 Wheel erfolgreich erstellt wird, die erforderlichen gebündelten Lizenztexte enthält und der Teststatus verstanden ist.