Use `dd` instead of `head -c`

[Bug #13538] [ruby-dev:50106]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58548 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

configure.in

@@ -4737,7 +4737,7 @@ AS_IF([test "`echo abcdefg hijklmno | fold -s -w10 | sed 1d`" = hijklmno], [FOLD
 AS_REQUIRE_SHELL_FN([config_summary],
     [AS_FUNCTION_DESCRIBE([config_summary], [NAME, VAL], [configuration summary])],
     [AS_IF([test -z "$2"], [], [
-	AS_ECHO_N(["   * $1:                     "]) | head -c26
+	AS_ECHO_N(["   * $1:                     "]) | dd bs=1 count=26 2>/dev/null
 	AS_IF([test "$FOLD"], [
 	    echo "$2" | fold -s -w50 |
 	    sed '1!s/^/                          /;$!s/$/\\/'