The issue happens on Silverblue where /home is a symlink to /var/home.
With this element-path is something like
/var/home/user/project/elements, when the project path is
/home/usr/project. Comparing canonical paths solves the issue.

Fixes #673

Backport to 1.2: Fix outside-of-project check when project path is not canonical.

See merge request !834