Allow for user path to solution wide json files

[MBulli]

Hi, I'm in a similar position where we use a custom build toolchain that regenerates solution and project files (not UE). Solution location is also temporary in my case and gets purged occasionally.

Could you add a more general option to specify a directory (ideally outside of the source tree) where args.json is stored? It could create a sub-directory in it for each solution path or something like that.

Originally posted by @chrisaverage in https://github.com/MBulli/SmartCommandlineArgs/issues/88#issuecomment-559538617