Fix compilation of server.cc on hpux.

Select and FD_ISSET are declared in sys/time.h on most versions
of hpux.  As a result, HAVE_PSELECT and HAVE_SELECT can be 0.

2023-01-08  John David Anglin  <danglin@gcc.gnu.org>

c++tools/ChangeLog:

	PR other/107616
	* server.cc (server): Don't call FD_ISSET when HAVE_PSELECT
	and HAVE_SELECT are zero.

c++tools/server.cc

@@ -753,8 +753,10 @@ server (bool ipv6, int sock_fd, module_resolver *resolver)
 		      }
 		  }
 
+#if defined (HAVE_PSELECT) || defined (HAVE_SELECT)
 	      if (active < 0 && sock_fd >= 0 && FD_ISSET (sock_fd, &readers))
 		active = -1;
+#endif
 	    }
 
 	  if (active >= 0)