helping you build you third wave infrastructure 是现在分词短语做后置定语,修饰最前面的名词短语foreign capital.
因为foreign capital和help之间为主动关系,所以用其现在分词形式.
该成分只是短语,并非定语从句,所以无须关系词引导.
再如：
Do you know the boy (standing under the tree)?现在分词短语做后置定语
= Do you know the boy (who is standing under the tree)?定语从句做后置定语,有关系代词who
你认识那个站在树下的男孩吗?