Webpack config not in strict mode, don't want to change the code

I trying to build production webpack of BitShares UI https://github.com/bitshares/bitshares-ui

The issue is that webpack is not running in strict mode I don't want to have to change the code though. Is there a way to force that webpack config is interpreted in strict mode so that I avoid this problem?

Step 13/19 : RUN npm run build
 ---> [Warning] Your kernel does not support swap limit capabilities or the cgroup is not mounted. Memory limited without swap.
 ---> Running in 7cfc6910af6a

 BitShares2-light@2.0.180108 build /build
 cross-env NODE_ENV=production webpack --env.prod

        let outputDir = env.electron ? "electron" : env.hash ? `hash-history_${baseUrl.replace("/", "")}` : "dist";

SyntaxError: Block-scoped declarations (let, const, function, class) not yet supported outside strict mode
    at exports.runInThisContext (vm.js:53:16)
    at Module._compile (module.js:374:25)
    at Object.Module._extensions..js (module.js:417:10)
    at Module.load (module.js:344:32)
    at Function.Module._load (module.js:301:12)
    at Module.require (module.js:354:17)
    at require (internal/module.js:12:17)
    at requireConfig (/build/node_modules/webpack/bin/convert-argv.js:97:18)
    at /build/node_modules/webpack/bin/convert-argv.js:104:17
    at Array.forEach (native)

npm ERR! Linux 4.13.0-26-generic
npm ERR! argv "/usr/bin/nodejs" "/usr/bin/npm" "run" "build"
npm ERR! node v4.2.6
npm ERR! npm  v3.5.2
npm ERR! BitShares2-light@2.0.180108 build: `cross-env NODE_ENV=production webpack --env.prod`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the BitShares2-light@2.0.180108 build script 'cross-env NODE_ENV=production webpack --env.prod'.
npm ERR! Make sure you have the latest version of node.js and npm installed.
npm ERR! If you do, this is most likely a problem with the BitShares2-light package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR!     cross-env NODE_ENV=production webpack --env.prod
npm ERR! You can get information on how to open an issue for this project with:
npm ERR!     npm bugs BitShares2-light
npm ERR! Or if that isn't available, you can get their info via:
npm ERR!     npm owner ls BitShares2-light
npm ERR! There is likely additional logging output above.

npm ERR! Please include the following file with any support request:
npm ERR!     /build/web/npm-debug.log
The command '/bin/sh -c npm run build' returned a non-zero code: 1