Fix for Linux compatibility

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@24650 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

configure.in

@@ -309,13 +309,14 @@ AC_PROG_LN_S
 AC_PROG_MAKE_SET
 AC_PROG_INSTALL
 AC_PROG_MKDIR_P
-if test "x$MKDIR_P" != "x -d"; then
-elif test x"$as_mkdir_p" != xfalse; then
+if test "x$MKDIR_P" = "x -d"; then
+  if test x"$as_mkdir_p" != xfalse; then
     MKDIR_P='mkdir -p'
     echo "use 'mkdir -p' as MKDIR_P"
   else
     AC_MSG_ERROR([mkdir -p is required])
   fi
+fi
 MAKEDIRS="$MKDIR_P"
 AC_SUBST(MAKEDIRS)