spec: Provide default-yama-scope.

spec: Provide default-yama-scope.

When yama is enabled in the kernel it might be used to filter any user
space access which requires PTRACE_MODE_ATTACH like ptrace attach, access
to /proc/PID/{mem,personality,stack,syscall}, and the syscalls
process_vm_readv and process_vm_writev which are used for interprocess
services, communication and introspection (like synchronisation, signaling,
debugging, tracing and profiling) of processes.

These are precisely the things that libdw dwfl and ebl backends rely on.
So make sure they don't mysteriously fail in such cases by providing the
default yama scope sysctl value.

This is implemented as a separate subpackage that just provides this
functionality so other packages that don't directly rely on elfutils-libs
can also just Requires: default-yama-scope to function properly.
https://bugzilla.redhat.com/show_bug.cgi?id=1209492#c69

Signed-off-by: Mark Wielaard <mjw@redhat.com>