add RIOT-OS support to WAMR (#425)

* add RIOT platform

see riot-os.org

* add simple RIOT example

product-mini/platforms/riot/Makefile

@@ -0,0 +1,96 @@
+APPLICATION = wamr-mini
+# If no BOARD is defined in the environment, use this default:
+BOARD ?= native
+
+# This has to be the absolute path to the RIOT base directory:
+RIOTBASE ?= $(CURDIR)/../../../../RIOT
+
+USEMODULE += xtimer
+USEMODULE += sema
+
+WPEDANTIC := 0
+WERROR := 0
+
+# Comment this out to disable code in RIOT that does safety checking
+# which is not needed in a production environment but helps in the
+# development process:
+DEVELHELP ?= 1
+
+# Change this to 0 show compiler invocation lines by default:
+QUIET ?= 1
+
+ARCHIVES += $(BINDIR)/libwamr.a
+
+#Load the usual RIOT make infastructure
+
+include $(RIOTBASE)/Makefile.include
+
+
+WAMR_SOURCE = $(CURDIR)/../../..
+WAMR_BUILD_DIR = $(BINDIR)/wamr
+
+#less Wall TODO: get things fixed
+CFLAGS :=  $(filter-out -pedantic, $(CFLAGS))
+CFLAGS += -Wno-format
+CFLAGS += -Wno-strict-prototypes
+CFLAGS += -Wno-old-style-definition
+CFLAGS += -Wno-cast-function-type
+
+WAMR_CORE = $(WAMR_SOURCE)/core
+IWASM_ROOT = $(WAMR_CORE)/iwasm
+SHARED_LIB_ROOT = $(WAMR_CORE)/shared
+
+IWASM_INCLUDES += ${IWASM_ROOT}/include \
+                   ${SHARED_LIB_ROOT}/platform/include \
+                   ${SHARED_LIB_ROOT}/platform/riot \
+
+
+INCLUDES += $(addprefix -I,${IWASM_INCLUDES})
+
+
+
+RIOT_INCLUDES = $(filter-out -%,$(subst -I,,$(INCLUDES)))
+
+#WAMR_BUILD_TARGET is "X86_32" "AARCH64[sub]", "ARM[sub]",
+#                     "THUMB[sub]", "MIPS" or "XTENSA"
+#no msp430, no AVR support for now
+
+#translate (CPU_ARCH) to Build Target
+ifeq ($(CPU),native)
+#$(CPU) is defined for every CPU
+#Riot native is x86_32
+	WAMR_BUILD_TARGET = X86_32
+else ifeq ($(findstring arm,$(CPU_ARCH)),arm)
+	WAMR_BUILD_TARGET = THUMB
+else ifeq ($(CPU_ARCH),mips32r2)
+	WAMR_BUILD_TARGET = MIPS
+else ifeq ($(CPU_ARCH),xtensa)
+	WAMR_BUILD_TARGET = XTENSA
+endif
+
+ifeq ($(QUIET), 0)
+	CMAKEMAKEFLAGS += VERBOSE=1
+endif
+
+
+$(BINDIR)/libwamr.a: $(WAMR_BUILD_DIR)/libwamr.a
+	cp $< $@
+
+$(WAMR_BUILD_DIR)/libwamr.a: $(WAMR_BUILD_DIR)/Makefile
+	$(MAKE) -C $(WAMR_BUILD_DIR) $(CMAKEMAKEFLAGS)
+
+$(WAMR_BUILD_DIR)/Makefile: CMakeLists.txt
+	cmake -B$(WAMR_BUILD_DIR) \
+		"-DRIOT_INCLUDES=$(RIOT_INCLUDES)"\
+		-DWAMR_ROOT_DIR=$(WAMR_SOURCE)\
+		-DWAMR_BUILD_TARGET=$(WAMR_BUILD_TARGET)\
+		-DCMAKE_SYSTEM_NAME=Generic \
+		-DCMAKE_SYSTEM_PROCESSOR="$(MCPU)" \
+		-DCMAKE_C_COMPILER=$(CC) \
+		-DCMAKE_C_COMPILER_WORKS=TRUE \
+
+print_build_target:
+	@echo CPU_ARCH: $(CPU_ARCH)
+	@echo CPU: $(CPU)
+	@echo CFLAGS: $(CFLAGS)
+	@echo WAMR_BUILD_TARGET: $(WAMR_BUILD_TARGET)