[haxe] add dom flag support

haxetool/haxe.js

@@ -89,6 +89,9 @@ class Haxe extends Sdk {
         fs.writeFileSync(path.resolve(buildDir, 'project.xml'), project);
 
         const args = ['-cwd', buildDir, 'run', 'openfl', command, platform];
+        if (config.flags.dom) {
+            args.push('-Ddom');
+        }
         if (debug) {
             args.push('-debug');
         }