cobalt/posix: Evaluate return code of signal_copyinfo extensions

They may fail as well, requiring us to return that code to the caller of
signal_wait.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kernel/cobalt/posix/signal.c

@@ -349,17 +349,18 @@ done:
 		ret = sys32_put_siginfo(u_si, sip, overrun);
 		if (!ret)
 			/* Allow an extended target to receive more data. */
-			cobalt_call_extension(signal_copyinfo_compat,
-					      &curr->extref, ret, u_si, sip,
-					      overrun);
+			ret = cobalt_call_extension(signal_copyinfo_compat,
+						    &curr->extref, ret, u_si,
+						    sip, overrun);
 	} else
 #endif
 	{
 		ret = signal_put_siginfo(u_si, sip, overrun);
 		if (!ret)
 			/* Allow an extended target to receive more data. */
-			cobalt_call_extension(signal_copyinfo, &curr->extref,
-					      ret, u_si, sip, overrun);
+			ret = cobalt_call_extension(signal_copyinfo,
+						    &curr->extref, ret, u_si,
+						    sip, overrun);
 	}
 
 out: