For scripts that use Python's standard argparse module to parse
command-line arguments, create a subclass which will show the usage
the usage information when a command-line parsing error occurs. The most
common case would be when the script is run with no arguments; at least
then the user immediately gets to see what arguments they might need to
pass instead of just an error message.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

Add a script to run "devtool modify" followed by a build on every target
recipe in the environment (with the option to skip/resume from/only
include specific recipes). This takes far too long to run as an
oe-selftest test but is still something that is useful to be able to
run. There's also a slightly quicker mode that just runs "devtool
extract" on each recipe.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>