Fix build-iso prerequisites

Move the PHONY tags to make them clearer to read.
Fix the clean rule so it deletes the build directory.

Makefile

@@ -1,31 +1,41 @@
-SOURCES = src/sched/spinlock.c src/debug/misc.c src/io/term/flanterm_backends/fb.c src/io/term/flanterm.c src/debug/panic.c src/debug/stacktrace.c src/boot/boot.c src/sched/scheduler.c src/sched/process.c src/mem/heap/kheap.c src/mem/paging/vmm.c src/mem/paging/paging.c src/mem/paging/pmm.c src/string/string.c src/io/kbd/ps2.c src/io/serial/serial.c src/io/term/term.c src/idt/idt.c src/mem/gdt/gdt.c src/mem/misc/utils.c src/time/timer.c src/kmain.c
 
+BUILDDIR := build
+ELFFILE := pepperk
+SRC := src
+SOURCES := $(shell find src -name '*.c')
+OBJFILES := $(patsubst $(SRC)/%.c, $(BUILDDIR)/%.o, $(SOURCES))
+
+CC := x86_64-elf-gcc
 CC_FLAGS=-Wall -Wextra -std=gnu99 -nostdlib -ffreestanding -fno-stack-protector -fno-omit-frame-pointer -fno-stack-check -fno-PIC -ffunction-sections -fdata-sections -mcmodel=kernel
 CC_PROBLEMATIC_FLAGS=-Wno-unused-parameter -Wno-unused-variable
 
-.PHONY: build build-iso debug debug2 run clean
+LD := x86_64-elf-ld
 
-build:
+$(ELFFILE): $(BUILDDIR) $(OBJFILES)
-	mkdir -p build
+	nasm -f elf64 src/idt/idt.S -o $(BUILDDIR)/idt_stub.o
-	rm -f *.o build/*.o
+	$(LD) -o $(ELFFILE) -T linker.ld $(OBJFILES) $(BUILDDIR)/idt_stub.o
-	x86_64-elf-gcc -g -c -Isrc $(SOURCES) $(CC_PROBLEMATIC_FLAGS) $(CC_FLAGS)
+	# Get the symbols for debugging
-	mv *.o build/
+	nm -n $(ELFFILE) | awk '$$2 ~ /[TtDdBbRr]/ {print $$1, $$3}' > symbols.map
-	nasm -f elf64 src/idt/idt.S -o build/idt_stub.o
-	x86_64-elf-ld -o pepperk -T linker.ld build/*.o
-	nm -n pepperk | awk '$$2 ~ /[TtDdBbRr]/ {print $$1, $$3}' > symbols.map
 	python3 symbols.py
-	nasm -f elf64 symbols.S -o build/symbols.o
+	nasm -f elf64 symbols.S -o $(BUILDDIR)/symbols.o
-	x86_64-elf-ld -o pepperk -T linker.ld build/*.o
+	$(LD) -o $(ELFFILE) -T linker.ld $(OBJFILES) $(BUILDDIR)/idt_stub.o
+
+$(BUILDDIR):
+	@mkdir -p $(BUILDDIR)
+
+$(BUILDDIR)/%.o: $(SRC)/%.c
+	mkdir -p $(dir $@)
+	$(CC) -g -c -Isrc $< $(CC_PROBLEMATIC_FLAGS) $(CC_FLAGS) -o $@
 
 limine/limine:
 	rm -rf limine
 	git clone https://github.com/limine-bootloader/limine.git --branch=v9.x-binary --depth=1
 	$(MAKE) -C limine
 
-build-iso: limine/limine build
+build-iso: limine/limine $(ELFFILE)
 	rm -rf iso_root
 	mkdir -p iso_root/boot
-	cp -v pepperk iso_root/boot
+	cp -v $(ELFFILE) iso_root/boot
 	mkdir -p iso_root/boot/limine
 	cp -v limine.conf iso_root/boot/limine
 	mkdir -p iso_root/EFI/BOOT
@@ -39,16 +49,20 @@ build-iso: limine/limine build
 		iso_root -o pepper.iso
 	./limine/limine bios-install pepper.iso
 
+.PHONY: debug
 debug:
 	/usr/bin/qemu-system-x86_64 -drive file=pepper.iso -s -S -d int -D qemu.log -no-reboot -no-shutdown &
-	gdb pepperk --command=debug.gdb
+	gdb $(ELFFILE) --command=debug.gdb
 
+.PHONY: debug2
 debug2:
 	/usr/bin/qemu-system-x86_64 -drive file=pepper.iso -s -S -d int -no-reboot -no-shutdown &
-	pwndbg pepperk --command=debug.gdb
+	pwndbg $(ELFFILE) --command=debug.gdb
 
+.PHONY: run
 run: build-iso
 	/usr/bin/qemu-system-x86_64 -cdrom pepper.iso -serial stdio
 
+.PHONY: clean
 clean:
-	rm -rf *.o symbols.map symbols.S pepperk iso_root pepper.iso limine build/*.o
+	rm -rf $(BUILDDIR) symbols.map symbols.S $(ELFFILE) iso_root pepper.iso limine