Hello,
on a Linux box I see:

options.c:772:2: warning: ignoring return value of ‘setuid’, declared with
attribute warn_unused_res
ult [-Wunused-result]
  setuid(getuid());
  ^~~~~~~~~~~~~~~~
options.c:773:2: warning: ignoring return value of ‘setgid’, declared with
attribute warn_unused_res
ult [-Wunused-result]
  setgid(getgid());
  ^~~~~~~~~~~~~~~~

Looking at the source, the reported calls are "extra" ones, they are
followed by proper setuid, setgid calls. I've found some way out from this
situation, of using the report value and reporting it (gmail paste, proper
patch is attached):

diff --git a/Src/options.c b/Src/options.c
index 590652ea9..e085af796 100644
--- a/Src/options.c
+++ b/Src/options.c
@@ -769,13 +769,23 @@ dosetopt(int optno, int value, int force, char
*new_opts)
     } else if(optno == PRIVILEGED && !value) {
        /* unsetting PRIVILEGED causes the shell to make itself
unprivileged */
 #ifdef HAVE_SETUID
-       setuid(getuid());
-       setgid(getgid());
+       int uerr = 0, gerr = 0;
+
+       if(setuid(getuid())) {
+           uerr = errno;
+       }
+       if(setgid(getgid())) {
+           gerr = errno;
+       }
         if (setuid(getuid())) {
             zwarn("failed to change user ID: %e", errno);
+            if (uerr)
+                zwarn("(error of additional preceding setuid() call: %e)",
uerr);
             return -1;
        } else if (setgid(getgid())) {
             zwarn("failed to change group ID: %e", errno);
+            if (gerr)
+                zwarn("(error of additional preceding setgid() call: %e)",
gerr);
             return -1;
         }
 #else