For some time now my auto builds of libSM, libXmu, libXt, and libXaw have been failing. These failures seemed to start with libSM and revolve around definitions found, or not found, in the header file uuid.h.
Google foo only revealed that the FreeBSD project had logged this problem as a bug, but it has been some time since this bug was reported with no relief in sight.
I did find a useful nugget which suggested that e2fsprog-libuuid should be used. A quick build of this package revealed that it conflicts, in that it installs to the same place, as ossp-uuid.
After removing the package ossp-uuid and installing e2fsprog-libuuid the build of libSM completed successfully.