Add help target to list available targets

platform/make.i386_pc

@@ -1,27 +1,44 @@
 $(srctree)/out/i386_pc/mop3.iso: $(srctree)/out/kernel.elf
-	rm -rf $(srctree)/out/i386_pc/tmp
-	mkdir -p $(srctree)/out/i386_pc/tmp
 	mkdir -p $(srctree)/out/i386_pc/tmp/iso/boot/grub
 	cp $(srctree)/out/kernel.elf $(srctree)/out/i386_pc/tmp/iso/boot
 	cp $(srctree)/platform/i386_pc/grub.cfg $(srctree)/out/i386_pc/tmp/iso/boot/grub
 	grub-mkrescue -o $(srctree)/out/i386_pc/mop3.iso $(srctree)/out/i386_pc/tmp/iso
 
-QEMU_EXTRA ?=
+boot ?= iso
 
-QEMU_OPTS := -M pc \
-						 -cdrom $(srctree)/out/i386_pc/mop3.iso \
-          	 -serial mon:stdio \
-						 $(QEMU_EXTRA)
+qemu_extra ?=
+
+qemu_opts := -M pc \
+             -serial mon:stdio \
+             $(QEMU_EXTRA)
+
+ifeq ($(boot),iso)
+qemu_opts += -cdrom $(srctree)/out/i386_pc/mop3.iso
+endif
 
 ifeq ($(debug),1)
-QEMU_OPTS += -gdb tcp::5557 -S
+qemu_opts += -gdb tcp::5557 -S
 endif
 
 i386_pc_qemu: $(srctree)/out/i386_pc/mop3.iso
-	qemu-system-i386 $(QEMU_OPTS)
+	qemu-system-i386 $(qemu_opts)
 
 i386_pc_bochs: $(srctree)/out/i386_pc/mop3.iso
 	rm -f $(srctree)/bochs.log
 	-bochs -f $(srctree)/platform/i386_pc/bochsrc.txt -q
 
-.PHONY: i386_pc_qemu i386_pc_bochs
+i386_pc_cleandirs:
+	rm -rf $(srctree)/out/i386_pc/tmp
+
+i386_pc_prepdirs:
+	mkdir -p $(srctree)/out/i386_pc/tmp
+
+i386_pc_images: i386_pc_cleandirs i386_pc_prepdirs \
+                $(srctree)/out/i386_pc/mop3.iso \
+                $(srctree)/out/i386_pc/mop3.img
+
+platform_clean: i386_pc_cleandirs
+	-rm -f $(srctree)/out/i386_pc/mop3.iso \
+		$(srctree)/out/i386_pc/mop3.img
+
+.PHONY: i386_pc_qemu i386_pc_bochs i386_pc_images platform_clean