From bug 29972: > The first build runs CodeGeneratorObjC.pm to generate the ObjC bindings, and > then checks if public interfaces changed (PublicDOMInterfaces.h). Since the API > of DOMHTMLAnchorElement changed, the script simply dies. (CodeGeneratorObjC.pm > line 297). > > The second time, the ObjC bindings are already generated, so there is no check > of SDK API, and the build succeeds. We likely need to remove the generated file that has the API failure, so it keeps getting rebuilt until resolved.