Previously the XAML Gated Build used to checkin the files belonging to multiple workspaces in TFS of differenct solution with one gated build definition only.
What i mean to say is like developers used to checkin multiples files in TFS with one gated build definition only, even though the workspaces of those files were not mapped in that old XAML Gated Build definition.
But after migrating to TFS 2017 update 3 it is not the same case here, we have to create separate gated build definition for each solutions present at different path in TFS. (Although i would say that this is a good practice and prevents any broken code to checked in TFS but its drawbacks is like multiple change-sets gets created for each solutions and files changes that we checkin)
To avoid multiple changesets issue one option is to create one gated build definition which will have workspace mapped for all the 8 solutions that we have and will get build and allow developers to checkin multiple files with one gated build definition but it also has it cons that the build time will get increase for no reasons and even if your are checkin one file it will build other solutions as well.
So is there any other option by which i can resolve this problem of allowing developers to checkin multiple files by one gated build itself and also maintain the code integrity checks at the same time?
No other better ways, actually the requirements are contradictory.
Generally create separate gated build definition for each solutions is the recommended way. But just as you said it has multiple changesets gets created...
If you have multiple solutions and have large amount of files mapped to a single workspace, then of course it will spent much more time on getting the sources and building...