Increase timeout for duchain gcc compatibility test

Summary:
This test depends on your system configuration and the presence of many headers.
Running the test in debug mode with address sanitizer can make it slow, so 5 seconds might not be enough.
In fact, it takes around ~10seconds here. Plus the test also fails on the CI because of the short timeout.

Increasing it to 60secs solves the problem for me.

Reviewers: #kdevelop, apol

Reviewed By: #kdevelop, apol

Subscribers: kdevelop-devel

Tags: #kdevelop

Differential Revision: https://phabricator.kde.org/D16541