[v9_8] add librt check for perftcpdns

contrib/perftcpdns/configure

@@ -2607,6 +2607,51 @@ _ACEOF
 
 fi
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for clock_gettime in -lrt" >&5
+$as_echo_n "checking for clock_gettime in -lrt... " >&6; }
+if ${ac_cv_lib_rt_clock_gettime+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_check_lib_save_LIBS=$LIBS
+LIBS="-lrt  $LIBS"
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char clock_gettime ();
+int
+main ()
+{
+return clock_gettime ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_lib_rt_clock_gettime=yes
+else
+  ac_cv_lib_rt_clock_gettime=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+LIBS=$ac_check_lib_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_rt_clock_gettime" >&5
+$as_echo "$ac_cv_lib_rt_clock_gettime" >&6; }
+if test "x$ac_cv_lib_rt_clock_gettime" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LIBRT 1
+_ACEOF
+
+  LIBS="-lrt $LIBS"
+
+fi
+
 
 case "$host" in
         *-freebsd*)

contrib/perftcpdns/configure.in

@@ -21,6 +21,7 @@ AC_PREREQ(2.13)
 AC_PROG_CC
 
 AC_CHECK_LIB(m, sqrt)
+AC_CHECK_LIB(rt, clock_gettime)
 
 case "$host" in
         *-freebsd*)