Add coredump support for ARCv3

[gmazurki]

When a process crashes it is often helpful to have its core dumped. The data gathered this way could be useful in a further investigation on the reason of the crash.

Currently we are unable to gather core dumps; only a simple stack trace is printed on the console. We have a HS58-based system.
This BUG is created to find out what prevents core dumps from functioning and to enable them, possibly as an option on demand.

We enabled:

In Linux:
CONFIG_COREDUMP
ELF_CORE

In busybox:
CONFIG_FEATURE_INIT_COREDUMPS

We checked that ulimit -a is unlimited.

What else is needed?