oh, might that be omitted in classic snaps then? This is from corebird which I’ve not done anything special:
#!/bin/sh
export PATH="$SNAP/usr/sbin:$SNAP/usr/bin:$SNAP/sbin:$SNAP/bin:$PATH"
export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:$SNAP/lib:$SNAP/usr/lib:$SNAP/lib/x86_64-linux-gnu:$SNAP/usr/lib/x86_64-linux-gnu"
export LD_LIBRARY_PATH="$SNAP/lib/x86_64-linux-gnu:$SNAP/usr/lib:$SNAP/usr/lib/x86_64-linux-gnu:$SNAP/usr/lib/x86_64-linux-gnu/pulseaudio:$LD_LIBRARY_PATH"
export LD_LIBRARY_PATH=$SNAP_LIBRARY_PATH:$LD_LIBRARY_PATH
exec "desktop-launch" libopenh264-launch pulse-launch gstreamer-launch $SNAP/usr/bin/corebird "$@"
The only line that I influenced by declarations in the snapcraft.yaml is the exec line. IIRC if you add an environment: declaration it will add those variables in this script before the exec, too.