setegid

pub fn setegid(egid: gid_t) usize {
    // We use setresgid here instead of setregid to ensure that the saved uid
    // is not changed. This is what musl and recent glibc versions do as well.
    //
    // The setresgid(2) man page says that if -1 is passed the corresponding
    // id will not be changed. Since gid_t is unsigned, this wraps around to the
    // max value in C.
    comptime assert(@typeInfo(uid_t) == .int and @typeInfo(uid_t).int.signedness == .unsigned);
    return setresgid(maxInt(gid_t), egid, maxInt(gid_t));
}