[PATCH][AArch64] Add unwind info to __libc_start_main

[Wilco Dijkstra]

Andreas Schwab wrote:

> >         * sysdeps/aarch64/Makefile: Build libc-start.c with -fexceptions.

> In which way is that specific to aarch64?  Why do you need exception
> support for unwinding (and not just -funwind-tables)?

It probably isn't - I just copied the code from ARM. But we could make
backtrace.c and libc-start.c always emit unwind tables on all targets.
I suppose -funwind-tables is sufficient in C code.

Wilco