Assert android.ApexModule interface for types having ApexModuleBase

Bug: 173472337
Test: m nothing
Change-Id: Idf1c6cb9fff6c18e34c4636e38a662ba4ff7d538
diff --git a/genrule/genrule.go b/genrule/genrule.go
index 93938c9..25b55e9 100644
--- a/genrule/genrule.go
+++ b/genrule/genrule.go
@@ -547,6 +547,9 @@
 	}
 }
 
+var _ android.ApexModule = (*Module)(nil)
+
+// Implements android.ApexModule
 func (g *Module) ShouldSupportSdkVersion(ctx android.BaseModuleContext,
 	sdkVersion android.ApiLevel) error {
 	// Because generated outputs are checked by client modules(e.g. cc_library, ...)