Hack in linux/ion.h

This is expected to be a system header file installed by libc.
The upstream libc we're using doesn't have it so hack it in.

Change-Id: I54c066eaa51c5736614fac1b41030b054da91a05
diff --git a/debian/control b/debian/control
index 14ccd02..ea93484 100644
--- a/debian/control
+++ b/debian/control
@@ -26,6 +26,7 @@
                libwayland-dev (>= 1.4.0) [linux-any],
                libdrm-dev (= 2.4.84+imx),
                wayland-protocols (>= 1.4) [linux-any] | wayland-protocols-imx (>= 1.13) [linux-any],
+               linux-headers-4.9.51-aiy (>=1),
                libvulkan-dev [linux-any],
                libgstreamer1.0-dev (>= 1.12.0),
                gstreamer1.0-plugins-base (>= 1.12.0),
diff --git a/debian/rules b/debian/rules
index eb95aec..458d1bf 100755
--- a/debian/rules
+++ b/debian/rules
@@ -105,8 +105,14 @@
 
 GST_PACKAGE_NAME := "GStreamer Bad Plugins"
 
+CFLAGS += -I$(shell realpath extinc)
+
 # setup links for packages
 pre-build::
+	# HACK in ion.h
+	mkdir -p extinc/linux
+	find /usr/src/*/include/uapi -name ion.h -exec cp {} extinc/linux \;
+
 	for p in $(PLUGINS); do \
 		rm -f debian/$(gst_pkgname)-$$p.install; \
 		sed \