UBUNTU: [Config] Force perf to use libiberty for demangling

UBUNTU: [Config] Force perf to use libiberty for demangling

Because libbfd is GPLv3 only and perf is GPLv2 only. Also this avoids
statically linking against libbfd to allow multiple versions of perf
being installed in parallel.

See: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=606050

BugLink: http://bugs.launchpad.net/bugs/783660

Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Andy Whitcroft <andy.whitcroft@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>