Add support for protoc plugins

Add a proto.plugin property to allow specifying a custom protoc
plugin to generate the code.

Fixes: 70706119
Test: m am StreamingProtoTest
Change-Id: I1ecdd346284b42bbcc8297019d98d2cd564eb94c
diff --git a/cc/cc_test.go b/cc/cc_test.go
index 8c0bcfe..05d74b9 100644
--- a/cc/cc_test.go
+++ b/cc/cc_test.go
@@ -54,6 +54,7 @@
 func createTestContext(t *testing.T, config android.Config, bp string, os android.OsType) *android.TestContext {
 	ctx := android.NewTestArchContext()
 	ctx.RegisterModuleType("cc_binary", android.ModuleFactoryAdaptor(BinaryFactory))
+	ctx.RegisterModuleType("cc_binary_host", android.ModuleFactoryAdaptor(binaryHostFactory))
 	ctx.RegisterModuleType("cc_library", android.ModuleFactoryAdaptor(LibraryFactory))
 	ctx.RegisterModuleType("cc_library_shared", android.ModuleFactoryAdaptor(LibrarySharedFactory))
 	ctx.RegisterModuleType("cc_library_static", android.ModuleFactoryAdaptor(LibraryStaticFactory))