If I try to omit the config file in the configuration of OpenOCD as a GDB-Server for a bare metal device I can not select this OpenOCD configuration as a GDB provider for a device. The solution to this would simply be to avoid checking for an empty config file in the isValid() function (see diff below). I've compiled QT-Creator with this simple patch and it works as expected now. It should be save to omit the check for an empty file because there already is a check in OpenOcdGdbServerProvider::arguments() (which also correctly omits a "-f" as an argument).
I have found a few more issues with the configuration of the bare metal plugin that are somewhat related to this one but will report them separately. By the way I'm really loving QT-Creator for bare metal development. It's awesome!
Since the autoformatting of this board completely screws up the (really small) diff I have also attached it. I've furthermore attached to screenshots to make clear what I mean. openocd_new_config.png shows a configuration that should also be allowed and which I also tested with the patch. Right now it only works the way shown in openocd_old_config.png, although one can omit the scripts path.