Allow to disable the New Architecture inside RN Tester (facebook#36895)

Summary:
Pull Request resolved: facebook#36895

Currently RN-Tester build with the New Architecture hardcoded to true.
For testing is convenient to disable it at times so we can test how the app behaves in the old arch.

Changelog:
[Internal] [Changed] - Allow to disable the New Architecture inside RN Tester

Reviewed By: cipolleschi

Differential Revision: D44917566

fbshipit-source-id: f1e6393e37bf6702677157b9577a26f0c4da0b86

Author: cortinico

packages/rn-tester/android/app/build.gradle

@@ -189,7 +189,9 @@ android {
         cmake {
             // RN Tester is doing custom linking of C++ libraries therefore needs
             // a dedicated CMakeLists.txt file.
-            path "src/main/jni/CMakeLists.txt"
+            if (project.property("newArchEnabled") == "true") {
+                path("src/main/jni/CMakeLists.txt")
+            }
         }
     }
 }
@@ -202,8 +204,10 @@ afterEvaluate {
     // As we're building 4 native flavors in parallel, there is clash on the `.cxx/Debug` and
     // `.cxx/Release` folder where the CMake intermediates are stored.
     // We fixing this by instructing Gradle to always mergeLibs after they've been built.
-    mergeHermesDebugNativeLibs.mustRunAfter(externalNativeBuildJscDebug)
-    mergeHermesReleaseNativeLibs.mustRunAfter(externalNativeBuildJscRelease)
-    mergeJscDebugNativeLibs.mustRunAfter(externalNativeBuildHermesDebug)
-    mergeJscReleaseNativeLibs.mustRunAfter(externalNativeBuildHermesRelease)
+    if (project.property("newArchEnabled") == "true") {
+        mergeHermesDebugNativeLibs.mustRunAfter(externalNativeBuildJscDebug)
+        mergeHermesReleaseNativeLibs.mustRunAfter(externalNativeBuildJscRelease)
+        mergeJscDebugNativeLibs.mustRunAfter(externalNativeBuildHermesDebug)
+        mergeJscReleaseNativeLibs.mustRunAfter(externalNativeBuildHermesRelease)
+    }
 }

packages/rn-tester/android/app/src/main/java/com/facebook/react/uiapp/RNTesterApplication.java

@@ -118,7 +118,7 @@ public List<ViewManager> createViewManagers(
 
         @Override
         protected boolean isNewArchEnabled() {
-          return true;
+          return BuildConfig.IS_NEW_ARCHITECTURE_ENABLED;
         }
 
         @Override
@@ -132,7 +132,9 @@ public void onCreate() {
     ReactFontManager.getInstance().addCustomFont(this, "Rubik", R.font.rubik);
     super.onCreate();
     SoLoader.init(this, /* native exopackage */ false);
-    DefaultNewArchitectureEntryPoint.load();
+    if (BuildConfig.IS_NEW_ARCHITECTURE_ENABLED) {
+      DefaultNewArchitectureEntryPoint.load();
+    }
     ReactNativeFlipper.initializeFlipper(this, getReactNativeHost().getReactInstanceManager());
   }