Revert^2 "add rust_toolchain_rustc_prebuilt module type"

400749d1f02c1751dbcaee540a17da945a513f62

Change-Id: I63f04e13605c43f800f01f45345e4b3dc61aefb7
diff --git a/cc/testing.go b/cc/testing.go
index d1632aa..dbdee9e 100644
--- a/cc/testing.go
+++ b/cc/testing.go
@@ -35,6 +35,7 @@
 
 	multitree.RegisterApiImportsModule(ctx)
 
+	ctx.RegisterModuleType("prebuilt_build_tool", android.NewPrebuiltBuildTool)
 	ctx.RegisterModuleType("cc_benchmark", BenchmarkFactory)
 	ctx.RegisterModuleType("cc_object", ObjectFactory)
 	ctx.RegisterModuleType("cc_genrule", GenRuleFactory)