[fix] AppImage: also include libsndio (#4487)

Should fix #4485.

Makefile

@@ -312,6 +312,8 @@ appimageupdate: all
 	ln -sf ../../resources/koreader.png $(INSTALL_DIR)/koreader
 	# TODO at best this is DebUbuntu specific
 	ln -sf /usr/lib/x86_64-linux-gnu/libSDL2-2.0.so.0 $(INSTALL_DIR)/koreader/libs/libSDL2.so
+	# required for our stock Ubuntu SDL even though we don't use sound
+	ln -sf /usr/lib/x86_64-linux-gnu/libsndio.so $(INSTALL_DIR)/koreader/libs/$(shell readlink /usr/lib/x86_64-linux-gnu/libsndio.so)
 ifeq ("$(wildcard $(APPIMAGETOOL))","")
 	# download appimagetool
 	wget "$(APPIMAGETOOL_URL)"

platform/appimage/AppRun

@@ -7,7 +7,7 @@ KOREADER_DIR="${0%/*}"
 # we're always starting from our working directory
 cd "${KOREADER_DIR}" || exit
 
-# export load library path for some old firmware
+# export load library path
 export LD_LIBRARY_PATH=${KOREADER_DIR}/libs:$LD_LIBRARY_PATH
 
 # export external font directory