make: provide BOARD, MCU and CPU name as a string

This PR adds the defined `RIOT_BOARD`, `RIOT_CPU` and `RIOT_MCU`.
They each are defined as `BOARD_${BOARD}`, `CPU_${CPU}`, and
`MCU_${CPU}`, resp.

`BOARD_${BOARD}` is defined as the string `"${BOARD}"`, but not in upper
case. Same for the other two.

Makefile.include

@@ -11,10 +11,6 @@ RIOTCPU := $(abspath $(RIOTCPU))
 RIOTBOARD ?= $(RIOTBASE)/boards
 RIOTBOARD := $(abspath $(RIOTBOARD))
 
-ifeq ($(strip $(MCU)),)
-	MCU = $(CPU)
-endif
-
 ifeq (,$(filter buildtest,$(MAKECMDGOALS)))
 	ifneq (,$(BOARD_WHITELIST))
 		ifeq (,$(filter $(BOARD),$(BOARD_WHITELIST)))
@@ -27,11 +23,6 @@ $(error This application does not run on following boards: $(BOARD_BLACKLIST))
 	endif
 endif
 
-# if you want to publish the board into the sources as an uppercase #define
-BB = $(shell echo $(BOARD)|tr 'a-z' 'A-Z'|tr '-' '_')
-CPUDEF = $(shell echo $(CPU)|tr 'a-z' 'A-Z'|tr '-' '_')
-CFLAGS += -DBOARD_$(BB) -DCPU_$(CPUDEF)
-
 BINDIRBASE ?= $(CURDIR)/bin
 BINDIR ?= $(abspath $(BINDIRBASE)/$(BOARD))/
 
@@ -50,6 +41,18 @@ include $(RIOTBOARD)/$(BOARD)/Makefile.include
 include $(RIOTCPU)/$(CPU)/Makefile.include
 include $(RIOTBASE)/Makefile.dep
 
+ifeq ($(strip $(MCU)),)
+	MCU = $(CPU)
+endif
+
+# if you want to publish the board into the sources as an uppercase #define
+BOARDDEF := $(shell echo $(BOARD) | tr 'a-z' 'A-Z' | tr '-' '_')
+CPUDEF := $(shell echo $(CPU) | tr 'a-z' 'A-Z' | tr '-' '_')
+MCUDEF := $(shell echo $(MCU) | tr 'a-z' 'A-Z' | tr '-' '_')
+CFLAGS += -DBOARD_$(BOARDDEF)='"$(BOARD)"' -DRIOT_BOARD=BOARD_$(BOARDDEF)
+CFLAGS += -DCPU_$(CPUDEF)='"$(CPU)"' -DRIOT_CPU=CPU_$(CPUDEF)
+CFLAGS += -DMCU_$(MCUDEF)='"$(MCU)"' -DRIOT_MCU=MCU_$(MCUDEF)
+
 # OSX fails to create empty archives. Provide a wrapper to catch that error.
 ifneq (0, $(shell mkdir -p $(BINDIR); $(AR) -rc $(BINDIR)empty-archive.a 2> /dev/null; echo $$?))
 	AR := $(RIOTBASE)/dist/ar-wrapper $(AR)

examples/hello-world/main.c

@@ -24,5 +24,9 @@
 int main(void)
 {
     puts("Hello World!");
+
+    printf("You are running RIOT on a(n) %s board.\n", RIOT_BOARD);
+    printf("This board features a(n) %s MCU.\n", RIOT_MCU);
+
     return 0;
 }