Patch required to avoid breakage

[Bruce Korb]

But I cannot determine what patch I need to fix it.
gnulib-tool installs a bunch of stuff in "lib/" that seems like
it ought to handle it, but I get this message anyway:

> No rule to make target '_Noreturn.h', needed by 'distdir-am'

I fixed it in one project by adding EXTRA_DIST += lib/_Noreturn.h
to the top level Makefile.am, but that seems like the wrong answer.
The "stdnoreturn" module should not be exposing its internal workings this way.