How to manually set Code Page and Collation for my SSAS Cube?
You have to change the collation settings either in your queries or in SSAS. There are several different options so the important question is do you use SSAS for other databases than the Croatian_CI_AS one.

If so you can pepper all your queries with collate Latin1_General_CI_AS to make sure that you get the data in the Latin1 collation into the cubes. If you are only using SSAS for the Croatian data, then change the SSAS collation to the same.