illumos gate

Build errors with gcc 9:

    ../../common/io/bpf/bpf.c: In function 'bpf_attachd':
    ../../common/io/bpf/bpf.c:253:6: error: 'error' may be used uninitialized in this function [-Werror=maybe-uninitialized]
      253 |  int error;
          |      ^~~~~

../../common/io/bpf/bpf.c: In function 'bpf_attachd':
../../common/io/bpf/bpf.c:317:12: error: 'bpr' may be used uninitialized in this function [-Werror=maybe-uninitialized]
  317 |  d->bd_mac = *bpr;
      |  ~~~~~~~~~~^~~~~~

    cc1: all warnings being treated as errors