Bug 950736 - Don't use target of included file to perform WebIDL codegen; r=ted

Make blissfully ignores failures when processing targets of "include"
directives. This was causing failures of WebIDL codegen to be ignored
and causing make to get in a loop.

--HG--
extra : rebase_source : 1231255705315319b308b4303bc3fc41237fbfa0
extra : amend_source : cfd801d7a3490a2a712994a60e548e3482a4992e