bugfix: forgot to create the directory <openresty-prefix>/site/lualib/.

util/configure

@@ -341,6 +341,8 @@ push @make_cmds, "cd $root_dir/build/$ngx_dir && "
 push @make_install_cmds, "cd $root_dir/build/$ngx_dir && "
     . "\$(MAKE) install DESTDIR=\$(DESTDIR)";
 
+push @make_install_cmds, "mkdir -p \$(DESTDIR)$prefix/site/lualib";
+
 if ($platform ne 'msys') {
     push @make_install_cmds, "ln -sf $ngx_prefix/sbin/nginx \$(DESTDIR)$prefix/bin/openresty";
 }