- Add the new EXTERNAL_BOARD_DIRS variable that can contain a space separated
list of folders containing external boards
- Introduce $(BOARDDIR) as shortcut for $(BOARDSDIR)/$(BOARD)
- Map the existing BOARDSDIR to the new approach
- If BOARDSDIR is provided by the user, it will be added to
EXTERNAL_BOARD_DIRS for backward compatibility. (And a warning is issued
to encourage users migrating to EXTRA_BOARDS.)
- BOARDSDIR is updated after the board is found to "$(BOARDDIR)/..".
- Useful for `include $(BOARDSDIR)/common/external_common/Makefile.dep`
- Provides backward compatibility
* Add a variable to list all boards without using 'find'.
* By default 'BOARDS' is the list of all boards.
* Add the 'info-boards' target that lists BOARDS.
* Use in RIOT/Makefile
