common: only FreeBSD has thread affinity compatible with Linux

src/common/thread.cpp:90:5: error: unknown type name 'cpu_set_t'; did you mean 'cpuset_t'?
    cpu_set_t cpu_set;
    ^~~~~~~~~
    cpuset_t
/usr/include/sys/_cpuset.h:48:24: note: 'cpuset_t' declared here
typedef struct _cpuset cpuset_t;
                       ^
1 error generated.