ci: fix x86 cross-compilation linker and artifact syntax ;

[gluonparticle]

Summary

As discussed in #502 , I've separated the immediate Maturin build fix from the OIDC in the PR ;

Changes

1. Installs gcc-multilib conditionally for the Linux x86 target, resolving the crti.o linker error that was preventing compilation.
2. Updates actions/download-artifact syntax to v4 with the required pattern: block to resolve the failing release download step.

Verification:
I ran an end-to-end mock release on my fork using a dummy tag.

• The x86 wheel compiles successfully (readelf confirms Class: ELF32).
• The v4 artifact step was sucessful, and
• The test suite clears successfully;

[gluonparticle]

Hi @scarlehoff, Sorry to bother you, could you please have a quick review on this isolated Maturin build fix from last week?

The x86 cross-compilation passed locally, please let me know if any changes are required! ;

[felixhekhorn]

Seems good. Thanks for the fix.