All the filenames are given in the stm32targets.xml. If they (whoever they might be) change the filename on the server(s) then we are .. doomed. Same if they decide to discontinue the server or just the files’ existence. Unless we had got all the zip archives offline on our hard drives. Tha’ts the only option I see..
There is one drawback, however - you’d have to check for possible updates - if the STL libs are/were still maintaned.. are they?