rust: Package shared libraries with fuzzer zips

Rust fuzzers were not packaging up their CC shared dependencies.
This would lead to fuzzers using the shared libraries included on
system, which may not be sanitized, leading to incorrect behavior.

This refactors the relevant code from CC and calls it from the Rust
build logic.

Bug: 202282599
Test: output rust fuzzer zip file includes shared dependencies.
Change-Id: I92196eb0141733797a67eae24f8e9aedea94c3bc