review: add comment

Author: inbelic

llvm/include/llvm/ObjCopy/DXContainer/DXContainerConfig.h

@@ -12,7 +12,9 @@
 namespace llvm {
 namespace objcopy {
 
-// DXContainer specific configuration for copying/stripping a single file.
+// DXContainer specific configuration for copying/stripping a single file. This
+// is defined, following convention elsewhere, as the return type of
+// `getDXContainerConfig`, which reports an error for an unsupported option.
 struct DXContainerConfig {};
 
 } // namespace objcopy