Docker Image: Increase thread stack size

Our docker image is based on Alpine, which has a lower default stack size for additional threads than other Linux distributions. This may cause trouble with authentication (and in fact, probably has caused crashes on the backup ladle server)

Details: https://ariadne.space/2021/06/25/understanding-thread-stack-sizes-and-how-alpine-is-different/

For 0.2.X, use the linker method. Can't be bothered to figure out how it works with ZThread. For Trunk, use the boost::thread constructor arguments.