[PATCH] Fix Ada bootstrap failure

[Arnaud Charlet]

> Given the nature of the work-around which makes Ada work again it's fairly
> sure that the Ada frontend does emit accesses to an alloca'ed area of
> memory even if its size is zero.  I.e. definitely a real bug.

Well, it's not clear whether it's the Ada frontend or the middle which is
emitting these, and until we have more info, it's hard to know whether it's
a real bug. Although sounds like there might indeed potentially be an issue.
I guess valgrind would detect and report this kind of issue?

Arno