Add another Debian libswscale-dev dependency for mod_av.

debian/resources/switch/source-release.sh

@@ -16,7 +16,7 @@ apt install -y pkg-config flac  libgdbm-dev libdb-dev gettext sudo equivs mlocat
 apt install -y liblua5.2-dev libtiff5-dev libperl-dev libcurl4-openssl-dev libsqlite3-dev libpcre3-dev
 apt install -y devscripts libspeexdsp-dev libspeex-dev libldns-dev libedit-dev libopus-dev libmemcached-dev
 apt install -y libshout3-dev libmpg123-dev libmp3lame-dev yasm nasm libsndfile1-dev libuv1-dev libvpx-dev
-apt install -y libavformat-dev
+apt install -y libavformat-dev libswscale-dev
 
 #install dependencies that depend on the operating system version
 if [ ."$os_codename" = ."stretch" ]; then