Remove the boards and shields lists from the 'usage' target output.
That might have been readable at some point long ago in Zephyr's
history, when only a few boards were available, but right now it's
obscuring the high level targets we really want 'usage' to print.
Instead, add 'boards' and 'shields' targets which the user can run to
get those lists, and reference them from the 'usage' output. This
makes 'usage' squintable again. We use the new list_boards.py script
from the 'boards' target.
Reference the 'help' target from 'usage' as well, and drop the
recommendation that people run '--target help' from the 'west build
--help' output for the 'west build --target' option. The canonical
place to look is 'usage' now.
Use the new list_boards.py code from 'west boards' as well, which
allows us to add the board's directory as a format string key, in
addition to its name and architecture.
Keep west-completion.bash up to date. While doing that, I noticed that
a bunch of references to this file refer to a stale location, so fix
those too.
Finally, the 'usage' output is what we print for a failed board or
shield lookup, so that needs to be updated also. Handle that by
invoking boards.cmake and a new shields.cmake in CMake script mode to
print the relevant output.
Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>
0d5e6c13e9