Skip test -e command

Summary: See above. Fails on unix systems since cmake replaces -e by -E.

Test Plan: No test needed. If it builds, everything is fine.

Reviewers: O1 MITK Core, kislinsk

Reviewed By: O1 MITK Core, kislinsk

Maniphest Tasks: T26252

Differential Revision: https://phabricator.mitk.org/D193