After mygui upgrade, a couple of include <memory> are needed to build with GCC.
Errors:
/wrkdirs/usr/ports/games/openmw/work/openmw-openmw-0.45.0/apps/openmw/mwgui/alchemywindow.hpp:78:14: error: 'unique_ptr' in namespace 'std' does not name a template type
std::unique_ptr<MWMechanics::Alchemy> mAlchemy;
^~~~~~~~~~/wrkdirs/usr/ports/games/openmw/work/openmw-openmw-0.45.0/apps/openmw/mwgui/alchemywindow.hpp:78:9: note: 'std::unique_ptr' is defined in header '<memory>'; did you forget to '#include <memory>'?
/wrkdirs/usr/ports/games/openmw/work/openmw-openmw-0.45.0/apps/openmw/mwgui/alchemywindow.hpp:14:1:
+#include <memory>
PR: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=237773