The following patch fixes the test to detect a working glibc regex api; there is no need to use --without-included-regex, and regoff_t is now defined properly, so it should work automagically.
Created attachment 83403 [details, diff] gnulib-regex.patch
added to 5.94-r2
And about dropping --without-included-regex, can it be done now? It causes coreutils to not compile on OpenBSD.
no ... on 64bit hosts it'll use the included regex still