Rust rlib vendor snapshot support.

Adds support for snapshotting Rust rlibs. This allows us
vendor-specific code that uses rlib-only linkage until dylib
snapshot support is added.

Bug: 184042776
Test: m nothing # new Soong tests pass
Test: Example test Rust vendor module builds
Test: m dist vendor-snapshot # includes rlibs
Change-Id: I4976d3e1efec0ee778cc97730d45be471dffb678

rust/Android.bp

@@ -32,6 +32,7 @@ bootstrap_go_package {
         "rust.go",
         "sanitize.go",
         "source_provider.go",
+        "snapshot_prebuilt.go",
         "snapshot_utils.go",
         "strip.go",
         "test.go",