Stop me if you've heard this one before :)
Given that pg_config --libdir yields "/usr/lib64"
to where/what would you expect
"AS '$libdir/uuid-ossp', 'uuid_generate_v5'"
to resolve?
The loader script,
~/tools/postgresql-8.4.2/contrib/uuid-ossp/uuid-ossp.sql, generates
"tools/postgresql-8.4.2/contrib/uuid-ossp/uuid-ossp.sql:9: ERROR: could
not access file "$libdir/uuid-ossp": No such file or directory"