Every so often I find myself wanting to debug UIKit and other system frameworks as part of tracking down an issue originally reported in WebKit. Although it is possible to build such system frameworks into the same build products directory as WebKit, subsequent builds of WebKit may fail due to compiler warnings (WebKit treats warnings as errors) when using headers from these frameworks. This is because Xcode treats all frameworks found in the build products directory as normal frameworks as opposed to system frameworks. I propose we establish a convention that frameworks placed under $(BUILT_PRODUCTS_DIR)/System/Library/Frameworks are treated as system frameworks and are preferred when building WebKit as a way to make it straightforward to build and debug WebKit with debug versions of other system frameworks.