At a meeting with the leaders of several construction and building trade unions, President Trump reiterated on Monday his interest in directing hundreds of billions of dollars to infrastructure investments, some of it from the federal government, union officials said. At the meeting, Mr. McGarvey raised one point of possible discord between the labor leaders and the Trump administration: the so-called Davis-Bacon Act, which requires the federal government to pay contractors and subcontractors “locally prevailing wages,” as determined by the Labor Department, on most construction or renovation projects.