Fix the setup to allow the build-from-source on host projects (#36702)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/36702

With the monorepo changes we broke the build from source for users.
This fixes it so that folks can just follow the guide:
https://reactnative.dev/contributing/how-to-build-from-source

Changelog:
[Android] [Fixed] - Fix the setup to allow the build-from-source on host projects

Reviewed By: cipolleschi

Differential Revision: D44502428

fbshipit-source-id: 3ad8fb114f5e2f7ffdf6fffa617ceaa45334f5f3

packages/react-native/build.gradle.kts

@@ -1 +1,18 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
 
+// This is the top level build.gradle.kts file used when the users
+// is doing a build from source. It's triggered as the user
+// will add an `includeBuild(../node_modules/react-native)` in
+// their settings.gradle.kts file.
+// More on this here: https://reactnative.dev/contributing/how-to-build-from-source
+plugins {
+  id("com.android.library") version "7.4.2" apply false
+  id("com.android.application") version "7.4.2" apply false
+  id("de.undercouch.download") version "5.0.1" apply false
+  kotlin("android") version "1.7.22" apply false
+}

packages/react-native/gradle.properties

@@ -0,0 +1 @@
+android.useAndroidX=true

packages/react-native/settings.gradle.kts

@@ -1 +1,31 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
 
+// This is the settings.gradle.kts file used when the users
+// is doing a build from source. It's triggered as the user
+// will add an `includeBuild(../node_modules/react-native)` in
+// their settings.gradle.kts file.
+// More on this here: https://reactnative.dev/contributing/how-to-build-from-source
+
+pluginManagement {
+  repositories {
+    mavenCentral()
+    google()
+    gradlePluginPortal()
+  }
+}
+
+rootProject.name = "react-native-github"
+
+include(":packages:react-native:ReactAndroid")
+
+project(":packages:react-native:ReactAndroid").projectDir = file("ReactAndroid/")
+
+include(":packages:react-native:ReactAndroid:hermes-engine")
+
+project(":packages:react-native:ReactAndroid:hermes-engine").projectDir =
+    file("ReactAndroid/hermes-engine/")