Fix a generic C99 compatibility issue in the generated configure
script, to avoid build failures with future compilers.
Current autoconf no longer generates this problematic code, so the
issue will go away once upstream re-runs autoconf.
diff --git a/configure b/configure
index 95d29da75706df9b..faf0bf5bfaf7a17d 100755
--- a/configure
+++ b/configure
@@ -760,7 +760,7 @@ cat > conftest.$ac_ext << EOF
#line 761 "configure"
#include "confdefs.h"
-main(){return(0);}
+int main(){return(0);}
EOF
if { (eval echo configure:766: \"$ac_link\") 1>&5; (eval $ac_link) 2>&5; } && test -s conftest${ac_exeext}; then
ac_cv_prog_cc_works=yes