Tweak the assert in ModuleBuilder from r224533 (PR21989)

Turns out there will be left-over deferred inline methods if there have
been errors, because in that case HandleTopLevelDecl bails out early.

llvm-svn: 224649

clang/lib/CodeGen/ModuleBuilder.cpp

@@ -64,8 +64,9 @@ namespace {
         M(new llvm::Module(ModuleName, C)) {}
 
     virtual ~CodeGeneratorImpl() {
-      assert(DeferredInlineMethodDefinitions.empty() &&
-             "Leftover inline method definitions!");
+      // There should normally not be any leftover inline method definitions.
+      assert(DeferredInlineMethodDefinitions.empty() ||
+             Diags.hasErrorOccurred());
     }
 
     llvm::Module* GetModule() override {