gulp: extend environment for tweego, but not replace it

gulpfile.js

@@ -135,7 +135,7 @@ function cleanupGit(cb) {
 	}
 }
 
-gulp.task('compileStory', shell.task(tweeCompileCommand(), {env: cfg.options.twee.environment, verbose: true}));
+gulp.task('compileStory', shell.task(tweeCompileCommand(), {env: {...process.env, ...cfg.options.twee.environment}, verbose: false}));
 
 const processors = {
 	"css": {