Add benchmark taget for root tests directory.
Add benchmark taget for root tests directory.

cmeon/ffjson,sunminghong/ffjson,pquerna/ffjson,xladykiller/ffjson,xiuzhifu/ffjson,jamesliu96/ffjson,trigrass2/ffjson,trigrass2/ffjson,jamesliu96/ffjson,cw2018/ffjson,pquerna/ffjson,xyliuke/ffjson,cmeon/ffjson,xladykiller/ffjson,xyliuke/ffjson,sunminghong/ffjson,xiuzhifu/ffjson,cw2018/ffjson