[app][mdebug] makefile.fw and linkscript to regenerate fw

The original tooling is lost to the mists of time and long-discarded
workstations, but this generates identical results and will enable
updating the code on the m0 sub-processor going forward.  Yay.

app/mdebug/fw-m0sub.ld

@@ -0,0 +1,32 @@
+
+/* RAM only binary layout */
+
+SECTIONS {
+	.text : {
+		. = ALIGN(4);
+		KEEP (*(.vectors))
+		*(.text)
+		*(.text.*)
+		*(.rodata)
+		*(.rodata.*)
+		. = ALIGN(4);
+		__data_init__ = . ;
+	} /* >RAM */
+	.data : {
+		. = ALIGN(4);
+		__data_start__ = . ;
+		*(.data)
+		*(.data.*)
+		. = ALIGN(4);
+		__data_end__ = . ;
+	} /* >RAM */
+	.bss : {
+		. = ALIGN(4);
+		__bss_start__ = . ;
+		*(.bss)
+		*(.bss.*)
+		*(COMMON)
+		. = ALIGN(4);
+		__bss_end__ = . ;
+	} /*>RAM */
+}

app/mdebug/makefile.fw

@@ -0,0 +1,26 @@
+
+TOOLCHAIN := /toolchain/arm-eabi-10.2.0/bin/arm-eabi-
+OBJCOPY := $(TOOLCHAIN)objcopy
+OBJDUMP := $(TOOLCHAIN)objdump
+CC := $(TOOLCHAIN)gcc
+
+CFLAGS := -mcpu=cortex-m0 -mthumb
+CFLAGS += -fno-builtin -nostdlib
+LFLAGS := -Wl,--script=fw-m0sub.ld -Wl,-Ttext=0x18000000
+
+all: zero.bin zero.lst fw-m0sub.h
+
+zero.elf: fw-m0sub.S
+	$(CC) $(CFLAGS) $(LFLAGS) -o $@ $<
+
+zero.lst: zero.elf
+	$(OBJDUMP) -D $< > $@
+
+zero.bin: zero.elf
+	$(OBJCOPY) -O binary $< $@
+
+fw-m0sub.h: zero.bin
+	xxd -i $< > $@
+
+clean:
+	rm -f zero.bin zero.lst zero.elf