Add a fat12-enabled boot sector

Makefile

@@ -9,17 +9,37 @@ crc16.s: crc16.c
 crc16.bin: crc16.s crt0.c
 	ia16-elf-gcc -o crc16.bin -Os -nostdlib crc16.s crt0.c
 
-wozmon.s: wozmon.cc
-	ia16-elf-gcc -S -Os -o wozmon.s wozmon.cc
+CC = ia16-elf-gcc
+CXX = ia16-elf-gcc
+LD = ia16-elf-gcc
+CXXFLAGS = -mregparmcall -ffunction-sections -Os -flto
+CFLAGS = -mregparmcall -ffunction-sections -Os -flto
+LDFLAGS = -mregparmcall -Wl,--gc-sections -Os -nostdlib -flto
 
-wozmon.bin: wozmon.s crt0.c
-	ia16-elf-gcc -o wozmon.bin -Os -nostdlib wozmon.s crt0.c
-	truncate -s 510 wozmon.bin
-	printf "\125\252" >> wozmon.bin
+%.elf:
+	$(LD) $(LDFLAGS) $(CPPFLAGS) -o $@ $^
+
+bootsectors = fat12boot.bin wozmon.bin
+
+$(bootsectors):
+	ia16-elf-objcopy -O binary $? $@
+	truncate -s 510 $@
+	printf "\125\252" >> $@
+
+fat12boot.elf: fat12boot.o fat12.o bootsect.S
+fat12boot.elf: LDFLAGS += -T bootsect.ld
+
+fat12boot.bin: fat12boot.elf
+
+wozmon.elf: wozmon.o bootsect.S
+wozmon.elf: LDFLAGS += -T bootsect.ld
+wozmon.elf: CPPFLAGS += -DNOBPB
+
+wozmon.bin: wozmon.elf
 
 .PHONY: clean
 clean:			## Remove generated files
-	rm -rf wozmon.bin crc16.bin readfloppy.bin writefloppy.bin
+	rm -rf wozmon.bin crc16.bin readfloppy.bin writefloppy.bin fat12boot.bin
 
 .PHONY: dev-image
 dev-image:
@@ -42,6 +62,7 @@ binaries:		## Build all binaries
 	docker build --build-arg TARGET=debug.bin -o . --target=export .
 	docker build --build-arg TARGET=dosdbt.bin -o . --target=export .
 	docker build --build-arg TARGET=format.bin -o . --target=export .
+	docker build --build-arg TARGET=fat12boot.bin -o . --target=export .
 
 
 .PHONY: help