symbols: fix CI check when in docker
Created by: chrismwendt
Continuation of #25421 which failed probably because there's no shared file system between the host and spawned containers.
We can't use -v because the spawned container might not share the same file system (e.g. when we're already inside docker and the spawned docker container will be a sibling on the host).
A workaround is to feed the file into the container via stdin:
'cat FILE | docker run ... -i ... sh -c "cat > FILE && ..."'