Fix how NODE_ENV is being handled

If an specific NODE_ENV value is specified, let it pass through and set the mode accordingly. If a non-standard NODE_ENV is specified, let is pass through and set the webpack mode to none.

lib/build.js

@@ -68,8 +68,14 @@ function webpackConfig(dir, additionalConfig) {
     defineEnv['process.env.' + key] = JSON.stringify(envConfig[key]);
   });
 
+  // Keep the same NODE_ENV if it was specified
+  var nodeEnv = process.env.NODE_ENV || 'production'
+
+  // Set webpack mode based on the nodeEnv
+  var webpackMode = ['production', 'development'].includes(nodeEnv) ? nodeEnv : 'none'
+
   var webpackConfig = {
-    mode: 'production',
+    mode: webpackMode,
     resolve: {
       extensions: ['.wasm', '.mjs', '.js', '.json', '.ts']
     },
@@ -99,6 +105,9 @@ function webpackConfig(dir, additionalConfig) {
       filename: '[name].js',
       libraryTarget: 'commonjs'
     },
+    optimization: {
+      nodeEnv
+    },
     devtool: false
   };
   fs.readdirSync(dirPath).forEach(function(file) {