lib/oe/image.py: Add image generation for companion debug filesystem
The companion debug filesystem, enabled with IMAGE_GEN_DEBUGFS, was
creating the companion filesystem but was missing the code to actually
package it into a usable filesystem.
The code (and associated documentation) will allow the debugfs to generate a
companion tarball or other image.
Signed-off-by: Mark Hatle <mark.hatle@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
