Make mkdir failsafe in case the directories are already present

util/mk1mf.pl

@@ -101,7 +101,7 @@ $out_def="out";
 $inc_def="outinc";
 $tmp_def="tmp";
 
-$mkdir="mkdir";
+$mkdir="-mkdir";
 
 ($ssl,$crypto)=("ssl","crypto");
 $ranlib="echo ranlib";