truffle-config.js

    compilers: {
        solc: {
            version: "0.6.6",
            settings: {          // See the solidity docs for advice about optimization and evmVersion
                optimizer: {
                  enabled: true,
                  runs: 999999
                },
                evmVersion: "istanbul", 
                outputSelection: {
                 "*": {
                   "": [
                     "ast"
                   ],
                   "*": [
                     "evm.bytecode.object",
                     "evm.deployedBytecode.object",
                     "abi",
                     "evm.bytecode.sourceMap",
                     "evm.deployedBytecode.sourceMap",
                     "metadata"
                   ]
                 },
               }
            }
        }
    }