devel/uatraits: fix build with GCC-based architectures

To link with boost, new GCC is needed on GCC architectures.

Add -L${OPENSSLLIB} only when OPENSSLLIB is not /usr/lib. Adding -L/usr/lib when using ports GCC makes GCC prefer /usr/lib/libstdc++.so instead of its own libstdc++, which makes the build fail.

PR: 239626
Approved by: mentors (implicit approval), daemon (maintainer, earlier version)