fix: don't let uglify-es inline functions with arguments

Fixes facebook#346.

This is a workaround for a bug in uglifyjs2
(mishoo/UglifyJS#2842), which can cause name
collisions when a function with arguments is inlined. This can cause an
unintended shadowing of a `var` or `let`, or a `TypeError: Assignment to
constant variable` in case of a `const`.

packages/react-scripts/config/webpack.config.prod.js

@@ -315,6 +315,9 @@ module.exports = {
           // Pending further investigation:
           // https://github.com/mishoo/UglifyJS2/issues/2011
           comparisons: false,
+          // Don't inline functions with arguments, to avoid name collisions:
+          // https://github.com/mishoo/UglifyJS2/issues/2842
+          inline: 1,
         },
         mangle: {
           safari10: true,