8151795: compiler/compilercontrol/parser/DirectiveParserTest.java fails with "assert failed: 0 != 0"

Treat zero added directives as fail

Reviewed-by: twisti, kvn

hotspot/src/share/vm/compiler/directivesParser.cpp

@@ -97,7 +97,7 @@ bool DirectivesParser::parse_from_file_inner(const char* filename, outputStream*
       buffer[num_read] = '\0';
       // close file
       os::close(file_handle);
-      return parse_string(buffer, stream) != -1;
+      return parse_string(buffer, stream) > 0;
     }
   }
   return false;