When a Bazel unittest crashes, its test archive can omit vendored dependencies built in external repositories and save shared libraries under names that differ from the core's module mappings. gather_failed_tests.py now downloads and collects these libraries under their runtime _solib names, keeping shared-library symbols beside the corresponding libraries. It preserves final library symlinks when separate debug is disabled and stages Windows DLLs beside executables and PDBs.

Regression tests cover external dependencies, libraries sharing a basename, transitioned configurations, symbol placement, Linux/macOS symlink chains, and Windows DLL placement.

Resolves SERVER-138924.