It would not infringe the right of Jews, because they would not be required to buy the meat, they would know that to them and for there purposes, just because its called kosher meat, does not mean its what they call kosher.
It doesn't matter that they wouldn't be required to buy the meat. It infringes on their right to freely exercise their religious beliefs, which do not include kosher pork! That would be making a mockery of their religious beliefs and customs, which is not permitted by the 1st Amendment, in my view. You have the personal right to make a mockery of their religious beliefs all day long, but the government has no such right to sanction the mockery.
You seem to think, the 1st only means that government can't prohibit someone from religious beliefs, and if that is the case, you need to read it again. Specifically, the second part, about the "free exercise thereof." I know it's tough for you to grasp the concept because it uses words you are not accustomed to, but it means that government can't pass laws which defile the customs, practices, and traditions of religion. These customs, practices, and traditions are a vital and fundamental part of their "free exercise" of religious belief. To remove or alter these customs, practices, and traditions, is to deny them the constitutional right they are promised by the 1st Amendment.
There are any number of absurd examples we could give, where government could restrict the free exercise of religion, without directly denying a person the right to worship. In fact, there isn't much the government COULD do, to stop people from worshiping whatever they feel like worshiping, is there? I mean, if you want to get technical about it, government could ban the Bible, and close down all churches, but people could still pray to God and worship Jesus, couldn't they? So, the 1st doesn't simply say the government can't prohibit you from worship, because nothing can really prohibit a human from worship, if they so desire. The 1st is a deeper protection than this, it protects the right to "freely exercise" through customs, practices, and traditions. For many religious groups, this includes the institution of marriage between a man and woman.