DWARF: add the config option

The DWARF unwinder is in place and ready. So introduce the config option
to allow users to enable it. It is by default off due to missing
assembly annotations.

And we now allow turning off FRAME_POINTERS if DWARF unwinder is
selected.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
3 files changed