[PATCH] Enable ARM tail calls for ELF

[Tim Northover]

> > My guess here is likely testing to be honest, i.e. not wanting to turn
> > on an untested code path by default.

> Yes.

Which is rather odd, since the compiler-specific (and complicated!)
part is tested routinely on iOS.
I know that when I last encountered it I was scared away more by the:

> // This option should go away when tail calls fully work.

than any real issues.

Tim