make_dev_ssd: add upstream cmdline flag for ptracers

The downstream patch adding the flags allowing ptracers to write to
proc/mem has been partly merged upstream. During the process, the
`foll_force` cmdline option was renamed to `proc_mem.force_override`,
with the `ptracer` option being now simply `ptrace`.

As the upstreamed patch has been backported to all stable kernel
branches, which are currently being imported into ChromeOS kernels, we
need to add this option to ensure debugging can still work on dev/test
images.

The previous version of this option will be removed at a later point,
once all ChromeOS kernels are up-to-date with the corresponding stable
branches.

BUG=b:325891891
TEST=Built prod/dev/test images and verify /proc/cmdline
BRANCH=main

Change-Id: Id4e340746b2c0938c889170cd7b1cfbfde8eceb0
Signed-off-by: Arnaud Ferraris <arnaud.ferraris@collabora.corp-partner.google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/5947523
Reviewed-by: Raul Rangel <rrangel@chromium.org>