Makefile.include: add multislot makefile

Makefile.include

 # include Makefile.local if it exists
 -include Makefile.local
 
-all:
+all: link
 
 # set undefined variables
 RIOTBASE       ?= $(dir $(lastword $(MAKEFILE_LIST)))
@@ -279,7 +279,7 @@ endif
 BASELIBS += $(BINDIR)/${APPLICATION}.a
 BASELIBS += $(APPDEPS)
 
-.PHONY: all clean flash term doc debug debug-server reset objdump help info-modules
+.PHONY: all link clean flash term doc debug debug-server reset objdump help info-modules
 .PHONY: ..in-docker-container
 
 ELFFILE ?= $(BINDIR)/$(APPLICATION).elf
@@ -293,17 +293,19 @@ LINKFLAGPREFIX ?= -Wl,
 
 DIRS += $(EXTERNAL_MODULE_DIRS)
 
+_LINK = $(if $(CPPMIX),$(CXX),$(LINK)) $(UNDEF) $(LINKFLAGPREFIX)--start-group $(BASELIBS) -lm $(LINKFLAGPREFIX)--end-group  $(LINKFLAGPREFIX)-Map=$(BINDIR)/$(APPLICATION).map $(LINKFLAGPREFIX)--cref $(LINKFLAGS)
+
 ifeq ($(BUILD_IN_DOCKER),1)
-all: ..in-docker-container
+link: ..in-docker-container
 else
 ## make script for your application. Build RIOT-base here!
-all: ..compiler-check ..build-message $(RIOTBUILD_CONFIG_HEADER_C) $(USEPKG:%=${BINDIR}/%.a) $(APPDEPS)
+link: ..compiler-check ..build-message $(RIOTBUILD_CONFIG_HEADER_C) $(USEPKG:%=${BINDIR}/%.a) $(APPDEPS)
 	$(Q)DIRS="$(DIRS)" "$(MAKE)" -C $(APPDIR) -f $(RIOTMAKE)/application.inc.mk
 ifeq (,$(RIOTNOLINK))
 ifeq ($(BUILDOSXNATIVE),1)
 	$(Q)$(if $(CPPMIX),$(CXX),$(LINK)) $(UNDEF) -o $(ELFFILE) $$(find $(BASELIBS) -size +8c) $(LINKFLAGS) $(LINKFLAGPREFIX)-no_pie
 else
-	$(Q)$(if $(CPPMIX),$(CXX),$(LINK)) $(UNDEF) -o $(ELFFILE) $(LINKFLAGPREFIX)--start-group $(BASELIBS) -lm $(LINKFLAGPREFIX)--end-group  $(LINKFLAGPREFIX)-Map=$(BINDIR)/$(APPLICATION).map $(LINKFLAGPREFIX)--cref $(LINKFLAGS)
+	$(Q)$(_LINK) -o $(ELFFILE)
 endif
 	$(Q)$(SIZE) $(ELFFILE)
 	$(Q)$(OBJCOPY) $(OFLAGS) $(ELFFILE) $(HEXFILE)
@@ -567,3 +569,6 @@ endif
 CFLAGS := $(patsubst -D%,,$(CFLAGS))
 CFLAGS := $(patsubst -U%,,$(CFLAGS))
 CFLAGS += -include '$(RIOTBUILD_CONFIG_HEADER_C)'
+
+# include multislot support
+include $(RIOTMAKE)/multislot.mk