buildmachine exclusive steam user:
see https://partner.steamgames.com/doc/sdk/uploading#Build_Account
buildmachine auth key (on mac)
./builder_osx/steamcmd +login $STEAM_USR $STEAM_PWD +quit
verify credentials cached locally work:
./builder_osx/steamcmd +login $STEAM_USR +quit
If succesfull this creates ~/Library/Application\ Support/Steam/config/config.vdf.
On a mac:
cp ~/Library/Application\ Support/Steam/config/config.vdf config.vdf
cat config.vdf | gzip | base64 | pbcopy
The gzipped and base64 encoded file is now in the clipboard and ready to be put into a CI secret.