On linux-aarch64 the conda gst-libav package has an unfixable ABI mismatch
(libdav1d.so.6 missing, libicuuc.so.78 via libxml2-16). Fix: use system
gstreamer1.0-libav installed via apt with GST_PLUGIN_PATH, and preload
system libgomp.so.1 to avoid static TLS block errors when dlopen loads
libgstlibav.so. avdec_h264 and avdec_aac now register correctly on device.
These vars are stored in conda activate.d/gst-env.sh and in deploy/run.sh.