Fixed build issue when DISABLE_FILESYSTEM is set.

Author: EmergReanimator

supervisor/supervisor.mk

@@ -35,6 +35,9 @@ CFLAGS += -DQSPI_FLASH_FILESYSTEM=$(QSPI_FLASH_FILESYSTEM)
 SPI_FLASH_FILESYSTEM ?= 0
 CFLAGS += -DSPI_FLASH_FILESYSTEM=$(SPI_FLASH_FILESYSTEM)
 
+DISABLE_FILESYSTEM ?= 0
+CFLAGS += -DDISABLE_FILESYSTEM=$(DISABLE_FILESYSTEM)
+
 ifeq ($(CIRCUITPY_BLEIO),1)
 	SRC_SUPERVISOR += supervisor/shared/bluetooth/bluetooth.c
   CIRCUITPY_CREATOR_ID ?= $(USB_VID)