rust: Add rustlibs auto dependency selection

Adds the rustlibs dependency type which will automatically select
between rlib and dylib based on the type of the library.

Bug: 143217452
Test: cd external/rust; mma
Change-Id: I97faadae98bf957090a32939cfb2d3a10f74a057

rust/test.go

@@ -105,6 +105,10 @@ func (test *testDecorator) compilerFlags(ctx ModuleContext, flags Flags) Flags {
 	return flags
 }
 
+func (test *testDecorator) autoDep() autoDep {
+	return rlibAutoDep
+}
+
 func init() {
 	// Rust tests are binary files built with --test.
 	android.RegisterModuleType("rust_test", RustTestFactory)