Linkerscript for `nrf52dk` has been updated to use `cortexm.ld` so does
not need the configuration anymore for the removed
`cpu/nrf52/ldscripts/nrf52832xxaa.ld`.
JLink flasher used by the only supported board `nrf52dk` has been updated.
FLASHFILE must now be defined by the board to use this in case a new one
wants to be supported.
The canned recipe is preferred to using $(FLASHER) $(FFLAGS) as it
allows to specify additional action actions (like what preflash is
currently doing.)
When doing `make -j clean all' the directories can be cleaned after
files are made. To ensure files are created after clean, those targets
are made conditionally dependent on the clean target.
This copies the handling done in Makefile.include.
