I would like that build_arguments support secrets

[DeaXStormZ]

Is your feature request related to a problem? Please describe.
I would need to wget -password=... a heavy file in the Dockerfile without showing the password. I would like to write RUN ./my-script.sh and wget in the script, but we cannot have have no access to the environment secrets in the script and the build_arguments does not support secrets.

Describe the solution you'd like
I would like that build_arguments support secrets

Describe alternatives you've considered
Downloading in the entrypoint.sh, but this would be done every time the job is run, whereas the other solution would allow to download only once during the build with a docker-image job