Separated run-grub and iso making

Now no need to rebuild iso if main binary wasn't changed

src/Makefile

@@ -61,7 +61,7 @@ clean:
 run:
 	qemu-system-$(ARCH) -kernel $(KERNELFILE) -serial stdio -S -s
 
-run-grub:
+$(ISOFILE): $(KERNELFILE)
 	mkdir -p $(BUILDDIR)/isodir
 	mkdir -p $(BUILDDIR)/isodir/boot
 	mkdir -p $(BUILDDIR)/isodir/boot/grub
@@ -73,5 +73,9 @@ run-grub:
 	echo '}' >> $(BUILDDIR)/isodir/boot/grub/grub.cfg 
 
 	grub-mkrescue -o $(ISOFILE) $(BUILDDIR)/isodir
+
+iso: $(ISOFILE)
+
+run-grub: iso
 	qemu-system-$(ARCH) -cdrom $(BUILDDIR)/orion.iso -serial stdio -S -s