Update configure.ac to use the default value of 64 for the cache line size

for systems which return a value of 0.

configure.ac

@@ -1496,7 +1496,7 @@ AC_INIT(configure.ac)
     AC_PATH_PROG(HAVE_GETCONF_CMD, getconf, "no")
     if test "$HAVE_GETCONF_CMD" != "no"; then
         CLS=$(getconf LEVEL1_DCACHE_LINESIZE)
-        if test "$CLS" != ""; then
+        if test "$CLS" != "" and "$CLS" != "0"; then
             AC_DEFINE_UNQUOTED([CLS],[${CLS}],[L1 cache line size])
         else
             AC_DEFINE_UNQUOTED([CLS],[64],[L1 cache line size])