Looking to drive an ST-Link in standalone mode
The ST-Link utility can be used to program a given file.

It supports S-Record, Bin, Hex and S19 files. You have to create one of those out of your .out-File using the IELFTOOL at the end of your build-process (can be automated, so your hex-file never goes out of sync).

The ST-Link utility has also a command line interface, so it can be integrated in automatic production programming.

It supports verification of the downloaded firmware, so you can set those options and it will check if the firmware was downloaded correctly, which is a nice feature to have in production.

The various return values for different errors allow for different actions to be taken automatically.