Also add a comment describing the reason for the override.
--- /dev/null
+# lib/firmware/kinect/ is indeed empty at package installation time, but this
+# is on purpose: the upstream Makefile creates the dir as a placeholder, and
+# then the kinect_fetch_fw script will copy the actual firmware there after
+# the user accepted the Microsoft EULA.
+kinect-audio-setup: package-contains-empty-directory lib/firmware/kinect/
+++ /dev/null
-kinect-audio-setup: package-contains-empty-directory lib/firmware/kinect/