With the players available, the strongest 11 is probably:
Marshall in goals.
Back 3 of Tierney, McTominey playing as an aggressive sweeper and Hanley
Patterson and Robertson as wingbacks
McGinn, Gilmour and Armstrong as the central midfielders.
Adams and Dykes up front.
---------------------Marshall-------------------------
------Hanley--------McTominey------Tierney-------
Patterson----------------------------------Robertson
------Armstrong----Gilmour----McGinn-------------
---------------Adams--------Dykes-------------------
Gives Scotland some width without having proper quality wide midfielders or attackers. Robertson isnt great defensively and Tierney behind him as the left sided defender of a back 3 gives him a bit of protection and uses Tierney in whats now his best position. McTominey can be flexible and that formation can change to a 4-4-2 or even a 4-4-1-1 with the 2 wingbacks dropping back, McTominey pushing into a defensive midfield role Adams can play off Dykes as a target man. Could even go 4-2-3-1 with Armstrong and Adams either side of Gilmour played as a central attacking midfielder.