openzeppelin-contracts/hardhat/skip-foundry-tests.js

const { subtask } = require('hardhat/config');
const { TASK_COMPILE_SOLIDITY_GET_SOURCE_PATHS } = require('hardhat/builtin-tasks/task-names');

subtask(TASK_COMPILE_SOLIDITY_GET_SOURCE_PATHS)
  .setAction(async (_, __, runSuper) =>
    (await runSuper()).filter((path) => !path.endsWith('.t.sol')),
  );