suexec cannot setgid

Issue

• suexec cannot setGID, strace log showing:

  [pid 111111] execve("/usr/sbin/suexec", ["/usr/sbin/suexec", "~12851", "1001", "test.cgi"], [/* 66 vars */]) = 0
  
  [pid 111111] socket(AF_LOCAL, SOCK_DGRAM|SOCK_CLOEXEC, 0) = 5
  [pid 111111] connect(5, {sa_family=AF_LOCAL, sun_path="/dev/log"}, 110) = 0
  [pid 111111] sendto(5, "<86>Jul 14 14:14:56 suexec[11111"..., 88, MSG_NOSIGNAL, NULL, 0) = 88
  [pid 111111] setgid(1001)              = -1 EPERM (Operation not permitted)
  [pid 111111] sendto(5, "<83>Jul 14 14:14:56 suexec[11111"..., 71, MSG_NOSIGNAL, NULL, 0) = 71
  [pid 111111] exit_group(109)            = ?
  [pid 111111] +++ exited with 109 +++