gitlab-ci: move check_missing_headers into its own job and hide the script

.gitlab/ci/check_missing_headers.sh

@@ -0,0 +1,28 @@
+#!/bin/sh
+
+# This script will tell you if there are headers in the source tree
+# that have not been installed in $PREFIX
+
+LIST=""
+
+for i in $(find spa/include -name '*.h' | sed s#spa/include/##);
+do
+	[ -f "$PREFIX/include/spa-0.2/$i" ] || LIST="$i $LIST"
+done
+
+for i in $(find src/pipewire -name '*.h' -a -not -name '*private.h' | sed s#src/##);
+do
+	[ -f "$PREFIX/include/pipewire-0.3/$i" ] || LIST="$i $LIST"
+done
+
+for i in $LIST;
+do
+	echo "$i not installed"
+done
+
+if [ "$LIST" != "" ];
+then
+	exit 1
+fi
+
+exit 0