merge current build context environment vars for lambda build

Author: shmargum

lib/build.js

@@ -16,6 +16,15 @@ function getBabelTarget(envConfig) {
 function webpackConfig(dir, additionalConfig) {
   var config = conf.load();
   var envConfig = config.build.environment || config.build.Environment || {};
+  var context = (
+    process.env.CONTEXT &&
+    config.context &&
+    config.context[process.env.CONTEXT] &&
+    (config.context[process.env.CONTEXT].environment || config.context[process.env.CONTEXT].Environment)
+  ) || {};
+  Object.keys(context).forEach(key => {
+    envConfig[key] = context[key];
+  });
   var babelOpts = { cacheDirectory: true };
   if (!fs.existsSync(path.join(process.cwd(), ".babelrc"))) {
     babelOpts.presets = [