[wip] xcframework build script

Author: okwasniewski

Apps/BRNPlayground/postinstall.js

@@ -30,7 +30,14 @@ function postInstall() {
   });
 
   if (os.platform() === "darwin") {
-    iosCMake();
+
+    exec("npx gulp buildIOSRNTA", {
+      cwd: "../../Package",
+    });
+
+    if (process.env.BUILD_BABYLON_FROM_SOURCE == "1") {
+      iosCMake();
+    }
 
     exec("npm install && npm run gulp buildIOSRNTA", {
       cwd: "../../Package",