newer gcc versions don't provide g77, so if it doesn't exist,
don't bother trying to test it (and failing)

http://bugs.gentoo.org/146592

--- autoconf-2.13/testsuite/autoconf.s/syntax.exp
+++ autoconf-2.13/testsuite/autoconf.s/syntax.exp
@@ -5,6 +5,10 @@
 set macros [exec sed -n $script $srcdir/../acspecific.m4]
 
 foreach mac $macros {
+    if { [string match "*F77*" "$mac"] && [catch {exec which g77} ignore_output] } then {
+        send_user "XFAIL: $mac\n"
+        continue
+    }
     send_user "$mac\n"
     autoconf_test $mac $mac
 }