arduino/sketches: build sketches as a module

Generate a module for arduino sketches in a subfolder of BINDIR.
This prevents issues when doing concurrent builds or out of tree build with
readonly sources.

This fixes RIOT-OS#5848

sys/arduino/Makefile.arduino_sketches.ink

@@ -0,0 +1,36 @@
+# Compile together the Arduino sketches of the application
+# They are declared a as new module in BINDIR
+SKETCHES = $(wildcard $(APPDIR)/*.sketch)
+
+# Head and tail for sketches outfile
+SNIPDIR         = $(RIOTBASE)/sys/arduino
+SKETCHES_ALL    = $(SNIPDIR)/pre.snip $(SKETCHES) $(SNIPDIR)/post.snip
+
+# Sketch module name and location
+SKETCH_MODULE  ?= arduino_sketches
+SKETCH_MOD_DIR ?= $(BINDIR)/$(SKETCH_MODULE)
+SKETCH_CPP     ?= $(APPLICATION)_sketches.cpp
+
+# Add dependency to the sketches module
+# Use `link` target to execute it before application makefile
+link: ..sketches_module
+USEMODULE += $(SKETCH_MODULE)
+DIRS      += $(SKETCH_MOD_DIR)
+
+.PHONY: ..sketches_module
+..sketches_module: $(SKETCH_MOD_DIR)/$(SKETCH_CPP) $(SKETCH_MOD_DIR)/Makefile
+
+# Building the module files
+$(SKETCH_MOD_DIR)/$(SKETCH_CPP): $(SKETCHES_ALL) | $(SKETCH_MOD_DIR)
+	@# Do not use $^ as Makefile is also a prerequisite
+	$(Q)cat $(SKETCHES_ALL) > $@
+$(SKETCH_MOD_DIR)/Makefile: | $(SKETCH_MOD_DIR)
+	$(Q)echo 'SRCXX = $(SKETCH_CPP)'               > $@
+	$(Q)echo 'include $$(RIOTBASE)/Makefile.base' >> $@
+$(SKETCH_MOD_DIR):
+	@mkdir -p $@
+
+# Make everything rebuild if current makefile changes
+CURMK = $(word $(words $(MAKEFILE_LIST)),$(MAKEFILE_LIST))
+$(SKETCH_MOD_DIR)/$(SKETCH_CPP): $(CURMK)
+$(SKETCH_MOD_DIR)/Makefile: $(CURMK)

sys/arduino/Makefile.include

@@ -1,9 +1,5 @@
-# compile together the Arduino sketches of the application
-SKETCHES = $(wildcard $(APPDIR)/*.sketch)
-SRCDIR = $(RIOTBASE)/sys/arduino
-
-# run the Arduino pre-build script
-$(shell $(RIOTBASE)/dist/tools/arduino/pre_build.sh $(SRCDIR) $(APPDIR) $(SKETCHES))
+# Add Arduino sketches to the application as a module
+include $(RIOTBASE)/sys/arduino/Makefile.arduino_sketches.ink
 
 # include the Arduino headers
 INCLUDES += -I$(RIOTBASE)/sys/arduino/include