Fix for building new architecture sources on Windows

On Windows there are limits on number of character in file paths and in command lines
Ref: https://android.googlesource.com/platform/ndk/+/master/docs/BuildSystemMaintainers.md#Path-Length-Limits
NDK allows circumventing command line limits using response(RSP) files as inputs using NDK_APP_SHORT_COMMANDS flag.

Windows can support long file paths if configured through registry or by prefixing all file paths with a special character sequence
The latter requires changes in NDK. And there are tools in NDK (AR) which is not able to handle long paths (>256) even after setting the registry key.
The new architecutre source tree is too deep, and the object file naming conventions in NDK makes the matters worse, by producing incredibly long file paths.
Other solutions such as symlinking source code etc. didn't work as expected, and makes the build scripts complicated and hard to manage.
This change temporarily works around the issue by placing the temporary build outputs as short a path as possible within the project path.

Changelog:
[Android] [Fixed] - Fix for building new architecture sources on Windows

ReactAndroid/build.gradle

@@ -318,6 +318,20 @@ android {
                     // This flag will suppress "fcntl(): Bad file descriptor" warnings on local builds.
                     arguments "--output-sync=none"
                 }
+
+                // Note: On Windows there are limits on number of character in file paths and in command lines
+                // Ref: https://android.googlesource.com/platform/ndk/+/master/docs/BuildSystemMaintainers.md#Path-Length-Limits
+                // NDK allows circumventing command line limits using response(RSP) files as inputs using NDK_APP_SHORT_COMMANDS flag.
+                // 
+                // Windows can support long file paths if configured through registry or by prefixing all file paths with a special character sequence 
+                // The latter requires changes in NDK. And there are tools in NDK (AR) which is not able to handle long paths (>256) even after setting the registry key.
+                // The new architecutre source tree is too deep, and the object file naming conventions in NDK makes the matters worse, by producing incredibly long file paths.
+                // Other solutions such as symlinking source code etc. didn't work as expected, and makes the build scripts complicated and hard to manage.
+                // This change temporarily works around the issue by placing the temporary build outputs as short a path as possible within the project path.
+                if (Os.isFamily(Os.FAMILY_WINDOWS)) {
+                    arguments "NDK_OUT=${rootProject.projectDir.getParent()}\\.cxx",
+                              "NDK_APP_SHORT_COMMANDS=true"
+                }
             }
         }
         ndk {

template/android/app/build.gradle

@@ -1,6 +1,7 @@
 apply plugin: "com.android.application"
 
 import com.android.build.OutputFile
+import org.apache.tools.ant.taskdefs.condition.Os
 
 /**
  * The react.gradle file registers a task for each build variant (e.g. bundleDebugJsAndAssets
@@ -157,6 +158,12 @@ android {
                     // Make sure this target name is the same you specify inside the
                     // src/main/jni/Android.mk file for the `LOCAL_MODULE` variable.
                     targets "helloworld_appmodules"
+
+                    // Fix for windows limit on number of character in file paths and in command lines
+                    if (Os.isFamily(Os.FAMILY_WINDOWS)) {
+                        arguments "NDK_OUT=${rootProject.projectDir.getParent()}\\.cxx",
+                            "NDK_APP_SHORT_COMMANDS=true"
+                    }
                 }
             }
         }