shellcheck: ignore SC2154 on NuttX

This is because NuttX uses a different assignment for variables.

ROMFS/CMakeLists.txt

@@ -179,6 +179,7 @@ if(SHELLCHECK_PATH)
 			--exclude=SC2086 # SC2086: Double quote to prevent globbing and word splitting.
 			--exclude=SC2039 # SC2039: In POSIX sh, == in place of = is undefined.
 			--exclude=SC2166 # SC2166: Prefer [ p ] || [ q ] as [ p -o q ] is not well defined.
+			--exclude=SC2154 # SC2154: <var> is referenced but not assigned (NuttX uses different asssignment)
 			init.d/*
 		DEPENDS ${romfs_gen_root_dir}/init.d/rc.autostart
 		WORKING_DIRECTORY ${romfs_gen_root_dir}