Make the reactNativeArchitectures property more discoverable

Summary:
I've unified the function that is responsible of getting the `reactNativeArchitectures` property
to a single one (ideally we could move it inside the Gradle Plugin in the future).
I've also added a property in the `gradle.properties` file. This makes easier for users to customize the
architecture to build without having to specify a CLI flag or edit multiple gradle files.

Changelog:
[Android] [Added] - Make the `reactNativeArchitectures` property more discoverable

Reviewed By: ShikaSD

Differential Revision: D32244997

fbshipit-source-id: 33180544400f9abe63e9b539ff16fefa17a024ba

Author: cortinico

gradle.properties

@@ -7,3 +7,8 @@ org.gradle.parallel=true
 ANDROID_NDK_VERSION=21.4.7075529
 android.useAndroidX=true
 kotlin_version=1.5.31
+
+# Use this property to specify which architecture you want to build.
+# You can also override it from the CLI using
+# ./gradlew <task> -PreactNativeArchitectures=x86_64
+reactNativeArchitectures=armeabi-v7a,arm64-v8a,x86,x86_64

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

@@ -135,9 +135,10 @@ def useIntlJsc = false
 /**
  * Architectures to build native code for.
  */
-def nativeArchitectures = project.getProperties().get("reactNativeArchitectures") ?
-                          project.getProperties().get("reactNativeArchitectures").split(",")
-                          : ["armeabi-v7a", "x86", "x86_64", "arm64-v8a"]
+def reactNativeArchitectures() {
+    def value = project.getProperties().get("reactNativeArchitectures")
+    return value ? value.split(",") : ["armeabi-v7a", "x86", "x86_64", "arm64-v8a"]
+}
 
 android {
     compileSdkVersion 29
@@ -185,7 +186,7 @@ android {
             enable enableSeparateBuildPerCPUArchitecture
             universalApk false
             reset()
-            include (*nativeArchitectures)
+            include (*reactNativeArchitectures())
         }
     }
     buildTypes {

template/android/app/build.gradle

@@ -123,9 +123,11 @@ def enableHermes = project.ext.react.get("enableHermes", false);
 /**
  * Architectures to build native code for.
  */
-def nativeArchitectures = project.getProperties().get("reactNativeArchitectures") ?
-                          project.getProperties().get("reactNativeArchitectures").split(",")
-                          : ["armeabi-v7a", "x86", "x86_64", "arm64-v8a"]
+def reactNativeArchitectures() {
+    def value = project.getProperties().get("reactNativeArchitectures")
+    return value ? value.split(",") : ["armeabi-v7a", "x86", "x86_64", "arm64-v8a"]
+}
+
 android {
     ndkVersion rootProject.ext.ndkVersion
 
@@ -143,7 +145,7 @@ android {
             reset()
             enable enableSeparateBuildPerCPUArchitecture
             universalApk false  // If true, also generate a universal APK
-            include (*nativeArchitectures)
+            include (*reactNativeArchitectures())
         }
     }
     signingConfigs {

template/android/gradle.properties

@@ -26,3 +26,8 @@ android.enableJetifier=true
 
 # Version of flipper SDK to use with React Native
 FLIPPER_VERSION=0.99.0
+
+# Use this property to specify which architecture you want to build.
+# You can also override it from the CLI using
+# ./gradlew <task> -PreactNativeArchitectures=x86_64
+reactNativeArchitectures=armeabi-v7a,arm64-v8a,x86,x86_64