Bjdooks/fix fpga bootrom makefile (#2969)

The prints after the command invocation makes it easier to work
out what went wrong if you get errors in the command, which end
up being done silently.

For testing, it is useful to be able to control where the CC and
OBJCOPY commands are coming from.

---------

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Co-authored-by: JeanRochCoulon <jean-roch.coulon@thalesgroup.com>

Author: bjdooks-ct

corev_apu/fpga/src/bootrom/Makefile

@@ -17,8 +17,8 @@ UART_BITRATE ?= 115200
 HAS_ETHERNET ?= 1
 endif
 
-CC = $(RISCV)/bin/${CROSSCOMPILE}gcc
-OBJCOPY = $(RISCV)/bin/$(CROSSCOMPILE)objcopy
+CC ?= $(RISCV)/bin/${CROSSCOMPILE}gcc
+OBJCOPY ?= $(RISCV)/bin/$(CROSSCOMPILE)objcopy
 SED = sed
 PLATFORM_DEFINES = -DCLOCK_FREQUENCY=$(CLOCK_FREQUENCY) -DUART_BITRATE=$(UART_BITRATE) -D$(PLATFORM)
 
@@ -65,12 +65,12 @@ $(MAIN): $(DTB) $(OBJS_C) $(OBJS_S) linker.lds
 	$(OBJCOPY) -O binary $< $@
 
 %.o: %.c
-	@$(CC) $(CFLAGS) $(INCLUDES) -c $<  -o $@
 	@echo "CC    <= $<"
+	@$(CC) $(CFLAGS) $(INCLUDES) -c $<  -o $@
 
 %.o: %.S
-	@$(CC) $(CFLAGS) $(CCASFLAGS) $(INCLUDES) -c $<  -o $@
 	@echo "CC    <= $<"
+	@$(CC) $(CFLAGS) $(CCASFLAGS) $(INCLUDES) -c $<  -o $@
 
 %.dts: %.dts.in
 	$(SED) -e "s/DRAM_SIZE_64/$(DRAM_SIZE_64)/g" \
@@ -85,8 +85,8 @@ $(MAIN): $(DTB) $(OBJS_C) $(OBJS_S) linker.lds
 	dtc -I dts $< -O dtb -o $@
 
 %.sv: %.img
-	./gen_rom.py $<
 	@echo "PYTHON >= $(MAIN_SV)"
+	./gen_rom.py $<
 
 clean:
 	$(RM) $(OBJS_C) $(OBJS_S) $(MAIN) $(MAIN_BIN) $(MAIN_IMG) *.dtb *.dts *.sv