Don't add DriverFramework dir for NuttX

I am unable to get the nuttx build dependencies set up so that
it builds the export dir before it builds df_driver_framework.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

src/firmware/nuttx/CMakeLists.txt

@@ -13,7 +13,7 @@ add_executable(firmware_nuttx
 set(nuttx_export_dir ${CMAKE_BINARY_DIR}/${BOARD}/NuttX/nuttx-export)
 
 set(link_libs
-	romfs apps nuttx m gcc
+	romfs apps nuttx m gcc df_driver_framework
 	)
 
 if(NOT ${BOARD} STREQUAL "sim")