build system: update terminology to control supported boards

[maribu]

Contribution description

This changes the terminology / variables used to control which boards are supported and unsupported by using self-explaining names. This should make it easier for people adopting RIOT who are not familiar with outdated terminology to understand what those variables control.

Testing procedure

$ make BOARD=native64 -C tests/drivers/edbg_eui                               
make: Entering directory '/home/maribu/Repos/software/RIOT/master/tests/drivers/edbg_eui'
The selected BOARD=native64 is not listed in BOARDS_SUPPORTED.
When the list BOARDS_SUPPORTED is not empty, only boards explicitly listed there are supported.
BOARDS_SUPPORTED = samr21-xpro
/home/maribu/Repos/software/RIOT/master/tests/drivers/edbg_eui/../../../Makefile.include:1034: *** You can let the build continue on expected errors by setting CONTINUE_ON_EXPECTED_ERRORS=1 to the command line.  Stop.
make: Leaving directory '/home/maribu/Repos/software/RIOT/master/tests/drivers/edbg_eui'

$ make BOARD=arduino-nano -C tests/sys/pthread_cleanup 
make: Entering directory '/home/maribu/Repos/software/RIOT/master/tests/sys/pthread_cleanup'
The selected BOARD=arduino-nano is listed in BOARDS_UNSUPPORTED.
BOARDS_UNSUPPORTED = arduino-nano arduino-duemilanove arduino-uno nucleo-f031k6 stm32f030f4-demo
/home/maribu/Repos/software/RIOT/master/tests/sys/pthread_cleanup/../../../Makefile.include:1034: *** You can let the build continue on expected errors by setting CONTINUE_ON_EXPECTED_ERRORS=1 to the command line.  Stop.
make: Leaving directory '/home/maribu/Repos/software/RIOT/master/tests/sys/pthread_cleanup'

$ make BOARD=arduino-mega2560 -C tests/sys/pthread_cleanup 
make: Entering directory '/home/maribu/Repos/software/RIOT/master/tests/sys/pthread_cleanup'
Building application "tests_pthread_cleanup" for "arduino-mega2560" with CPU "atmega2560".

[...]
   text	   data	    bss	    dec	    hex	filename
  15000	    318	   1366	  16684	   412c	/home/maribu/Repos/software/RIOT/master/tests/sys/pthread_cleanup/bin/arduino-mega2560/tests_pthread_cleanup.elf

Issues/PRs references

None

[riot-ci]

Murdock results

✔️ PASSED

4eaa408 fixup! build system: update terminology to control supported boards

Success	Failures	Total	Runtime
11004	0	11005	12m:01s

Artifacts

• Documentation preview