The ProjectGUID of WebKit2 windows project is the same as the one in the WebKit project. GUIDs should be unique across projects.
Created attachment 57045 [details] Patch
Fixed in http://trac.webkit.org/changeset/60183
http://trac.webkit.org/changeset/60183 might have broken GTK Linux 64-bit Release The following changes are on the blame list: http://trac.webkit.org/changeset/60184 http://trac.webkit.org/changeset/60182 http://trac.webkit.org/changeset/60183