Nicer error for NDK non-generic list.

Fixes: 147479301
Test: fuzzer (corpus added)
Change-Id: I3cc2960d6232c332aa96627726cb3bc449987465
diff --git a/aidl_language.cpp b/aidl_language.cpp
index 92571ad..8146502 100644
--- a/aidl_language.cpp
+++ b/aidl_language.cpp
@@ -742,9 +742,9 @@
 
 // TODO: we should treat every backend all the same in future.
 bool AidlTypeSpecifier::LanguageSpecificCheckValid(Options::Language lang) const {
-  if (lang == Options::Language::CPP) {
+  if (lang != Options::Language::JAVA) {
     if (this->GetName() == "List" && !this->IsGeneric()) {
-      AIDL_ERROR(this) << "List without type isn't supported in cpp.";
+      AIDL_ERROR(this) << "Currently, only the Java backend supports non-generic List.";
       return false;
     }
   }