make/tools: added shared script+mk for using BOSSA

Makefile.include

@@ -367,6 +367,9 @@ flash: all $(FLASHDEPS)
 		exit 1; }
 	$(FLASHER) $(FFLAGS)
 
+preflash: all
+	$(PREFLASHER) $(PREFFLAGS)
+
 term: $(filter flash, $(MAKECMDGOALS))
 	@command -v $(TERMPROG) >/dev/null 2>&1 || \
 		{ $(COLOR_ECHO) \
@@ -430,6 +433,10 @@ include $(RIOTMAKE)/features.inc.mk
 # Export variables used throughout the whole make system:
 include $(RIOTMAKE)/vars.inc.mk
 
+# Include build targets for selected tools after the default RIOT targets have
+# been defined (-> so the `all` will be always the first target)
+include $(RIOTMAKE)/tools/targets.inc.mk
+
 # Warn if the selected board and drivers don't provide all needed features:
 ifneq (, $(filter all, $(if $(MAKECMDGOALS), $(MAKECMDGOALS), all)))
   EXPECT_ERRORS :=

makefiles/tools/bossa.inc.mk

@@ -0,0 +1,26 @@
+export FLASHER ?= $(RIOTBASE)/dist/tools/bossa/bossac
+export FFLAGS  ?= -p $(PORT) -i -i -w -v -b -R $(HEXFILE)
+
+export OFLAGS  = -O binary
+export HEXFILE = $(ELFFILE:.elf=.bin)
+
+# some arduino boards need to toggle the serial interface a little bit to get
+# them ready for flashing...
+ifneq (,$(BOSSA_ARDUINO_PREFLASH))
+OS := $(shell uname)
+ifeq ($(OS),Linux)
+  STTY_FLAG = -F
+else ifeq ($(OS),Darwin)
+  STTY_FLAG = -f
+endif
+
+PREFLASHER ?= stty
+PREFFLAGS  ?= $(STTY_FLAG) $(PORT) raw ispeed 1200 ospeed 1200 cs8 -cstopb ignpar eol 255 eof 255
+FLASHDEPS += preflash
+endif
+
+# if we go with the default (BOSSA shipped with RIOT), we download and build
+# the tool if not already done
+ifeq ($(RIOTBASE)/dist/tools/bossa/bossac,$(FLASHER))
+FLASHDEPS += $(RIOTBASE)/dist/tools/bossa/bossac
+endif

makefiles/tools/targets.inc.mk

@@ -0,0 +1,11 @@
+# This file contains a collection of targets defined by tools shipped with RIOT.
+# The reason for keeping those targets separated from their tool Makfiles is
+# that these targets have to be defined after the default build targets
+# (as `all`), so `all` will always be the first target defined and thereby the
+# default target when `make` is called without any further argument.
+
+# target for building the bossac binary
+$(RIOTBASE)/dist/tools/bossa/bossac:
+	@echo "[INFO] bossac binary not found - building it from source"
+	@make -C $(RIOTBASE)/dist/tools/bossa
+	@echo "[INFO] bossac binary successfully build!"