Allow using default initramfs with INITRD=1

Author: gsingh93

Makefile

@@ -329,8 +329,11 @@ QEMU_ARGS := \
   $(QEMU_EXTRA_ARGS)
 
 ifneq ($(INITRD),)
-  QEMU_ARGS += -initrd $(INITRD)
+  ifeq ($(INITRD),1)
+    INITRD := $(CPIO_FILE)
+  endif
   QEMU_EXTRA_KERNEL_CMDLINE += rdinit=$(RDINIT)
+  QEMU_ARGS += -initrd $(INITRD)
 else
   QEMU_ARGS += -drive file=$(ROOTFS),if=virtio,format=$(ROOTFS_FORMAT)
   QEMU_EXTRA_KERNEL_CMDLINE += root=/dev/vda