autotests: do not incorrectly split spaces in paths of duplicate results

Summary:
Now using a hand-made loop to avoid the dependency on kcoreaddons
introduced by the earlier commit.

Test Plan: bin/dupes from a srcdir with a space, after duplicating one icon

Reviewers: sitter, apol

Reviewed By: sitter

Subscribers: cfeck, Frameworks

Differential Revision: https://phabricator.kde.org/D9807