Fix CI: set LD_LIBRARY_PATH for auditwheel to find libarrow

auditwheel needs to locate libarrow.so.2400 on the library path
to bundle it into the repaired wheel.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: rustyconover

.github/workflows/build-slim-wheels.yml

@@ -210,6 +210,7 @@ jobs:
           # Repair wheel (bundles system deps, tags as manylinux)
           pip install auditwheel
           mkdir -p /tmp/repaired
+          export LD_LIBRARY_PATH="/tmp/arrow-dist/lib:${LD_LIBRARY_PATH:-}"
           auditwheel repair "$WHEEL_PATH" -w /tmp/repaired/
 
           # Copy to output