ConfigurationBuildDir includes should precede WebKitLibraries. This is because some files in the newer WebKitLibaries versions have overlapping files "include/private/wtf". These files will not necessarily match up with whatever is on ToT since new WebKitLibraries are only released periodically. This caused build issues when using a newer WebKitLibraries version, specifically in JSC. JSC should prioritize the files in the build directory which are copied from ToT when searching for file includes. This might also be an issue in other projects down the road but I think taking a "fix it as they come" approach is better here.
Created attachment 186138 [details] patch
Comment on attachment 186138 [details] patch rubberstamped by thorton
http://trac.webkit.org/changeset/141921