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.

Inizia leggendo il workflow aggiunto in #481 e la configurazione di build del wheel di LightGBM 4.7.0. Riproduci la build e la riparazione con auditwheel, poi segui #617 per capire il segfault del ranking-test. Il lavoro è completo quando un wheel riscv64 viene compilato correttamente, include i testi di licenza raggruppati richiesti e lo stato dei test è compreso.