Skip animations tests for MinGW.

These tests typically fail in the CI.
Task-number: QTBUG-36290

Change-Id: I36a19c2914932d4f70c1df24e1c5ad4a3d0e2795
Reviewed-by: Tony Sarajärvi <tony.sarajarvi@digia.com>
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>
Reviewed-by: Alan Alpert <aalpert@blackberry.com>