Minor fix for illumos support

illumos is the opensource continuation of OpenSolaris after Oracle
closed to source it (again).

For example use see: openbao/openbao#205.

Signed-off-by: Jasper Siepkes <siepkes@serviceplanet.nl>

pkg/system/stat_illumos.go

@@ -0,0 +1,15 @@
+package system // import "github.com/docker/docker/pkg/system"
+
+import "syscall"
+
+// fromStatT converts a syscall.Stat_t type to a system.Stat_t type
+func fromStatT(s *syscall.Stat_t) (*StatT, error) {
+	return &StatT{
+		size: s.Size,
+		mode: uint32(s.Mode),
+		uid:  s.Uid,
+		gid:  s.Gid,
+		rdev: uint64(s.Rdev),
+		mtim: s.Mtim,
+	}, nil
+}