ADD: improve Makefile in tests/, add explicit arch flags

tests/Makefile

@@ -1,24 +1,46 @@
-GCC=riscv64-unknown-elf-gcc
-OBJDUMP=riscv64-unknown-elf-objdump
-CFLAGS= -std=gnu99 -O2 -fno-common -fno-builtin-printf -Wall
-LDFLAGS= -static
+#################################
+# RISCV Toolchain
+#################################
+
+PREFIX = riscv64-unknown-elf-
+
+GCC = $(PREFIX)gcc
+CXX = $(PREFIX)g++
+CP = $(PREFIX)objcopy
+OBJDUMP = $(PREFIX)objdump
+DG = $(PREFIX)gdb
+SIZE = $(PREFIX)size
+
+
+#################################
+# Flags
+#################################
+
+# SoC Settings
+ARCH = rv64imafdc
+ABI = lp64d
+ARCHFLAGS = -march=$(ARCH) -mabi=$(ABI)
+
+CFLAGS  = -std=gnu99 -O2 -fno-common -fno-builtin-printf -Wall
+CFLAGS += $(ARCHFLAGS)
+LDFLAGS = -static
 
 include libgloss.mk
 
 PROGRAMS = pwm blkdev accum charcount nic-loopback big-blkdev pingd \
            streaming-passthrough streaming-fir nvdla spiflashread spiflashwrite fft gcd \
            hello
 
-spiflash.img: spiflash.py
-	python3 $<
 
 .DEFAULT_GOAL := default
 
-.PHONY: default
-default: $(addsuffix .riscv,$(PROGRAMS)) spiflash.img
 
-.PHONY: dumps
-dumps: $(addsuffix .dump,$(PROGRAMS))
+#################################
+# Build
+#################################
+
+spiflash.img: spiflash.py
+	python3 $<
 
 %.o: %.S
 	$(GCC) $(CFLAGS) -D__ASSEMBLY__=1 -c $< -o $@
@@ -33,7 +55,17 @@ dumps: $(addsuffix .dump,$(PROGRAMS))
 	$(OBJDUMP) -D $< > $@
 
 
+#################################
+# Recipes
+#################################
+
 .PHONY: clean
 clean:
 	rm -f *.riscv *.o *.dump
 	$(if $(libgloss),rm -rf $(libgloss_builddir)/)
+
+.PHONY: default
+default: $(addsuffix .riscv, $(PROGRAMS)) spiflash.img
+
+.PHONY: dumps
+dumps: $(addsuffix .dump, $(PROGRAMS))