Rust: Vendor support for Rust static libraries.

We don't have Rust VNDK support yet, but static linkage can be
supported in the interim. This adds support for making rust_ffi_static
libraries available to CC vendor modules.

Since rust_ffi_static modules will link against rlibs, we allow rlib
linkage into vendor as well, but only for the variants which use the
rlib libstd.

Bug: 172525289
Test: New Soong tests pass
Test: Example vendor cc_binary links against rust_ffi_static module.
Change-Id: Idf3aeb51e32293866f1ad965e329aa6b9e0bf2ef
diff --git a/rust/Android.bp b/rust/Android.bp
index 8618207..df731db 100644
--- a/rust/Android.bp
+++ b/rust/Android.bp
@@ -15,6 +15,7 @@
         "clippy.go",
         "compiler.go",
         "coverage.go",
+        "image.go",
         "library.go",
         "prebuilt.go",
         "proc_macro.go",
@@ -33,6 +34,7 @@
         "clippy_test.go",
         "compiler_test.go",
         "coverage_test.go",
+        "image_test.go",
         "library_test.go",
         "project_json_test.go",
         "protobuf_test.go",