fix(android): allow overriding CMake version for Windows long-path builds (#265)

Fixes #263

On Windows, the Android build fails when CMake object-file paths exceed
`MAX_PATH` (260 chars). The NDK default CMake (3.22.1) can't handle the
deeply-nested paths from Nitrogen's generated sources.

This is a [known issue across React Native libraries that use
CMake](https://docs.swmansion.com/react-native-reanimated/docs/guides/building-on-windows/).
Adds support for the `CMAKE_VERSION` env var (same as Reanimated) so
users can opt into a newer CMake (e.g. 3.31.6) that handles long paths.

Author: mfazekas

README.md

@@ -131,6 +131,10 @@ export default {
 
 </details>
 
+## Building on Windows (CMake long-path failures)
+
+On Windows, the Android build can fail with `ninja: error: mkdir(CMakeFiles/rive.dir/...): No such file or directory` due to the Windows `MAX_PATH` (260-character) limit. This is a [known issue across React Native libraries that use CMake](https://docs.swmansion.com/react-native-reanimated/docs/guides/building-on-windows/). Set `CMAKE_VERSION` to a newer version (e.g. `3.31.6`) before building — see the Reanimated docs for full setup instructions.
+
 ## Error Handling
 
 All Rive operations can be wrapped in try/catch blocks for error handling, for example, loading a file:

android/build.gradle

@@ -69,6 +69,13 @@ android {
   externalNativeBuild {
     cmake {
       path "CMakeLists.txt"
+      // On Windows the NDK default CMake (3.22.1) fails when object-file
+      // paths exceed MAX_PATH (260 chars). Set CMAKE_VERSION=3.31.6 to fix.
+      // See: https://docs.swmansion.com/react-native-reanimated/docs/guides/building-on-windows/
+      def cmakeVersionOverride = System.getenv("CMAKE_VERSION")
+      if (cmakeVersionOverride) {
+        version cmakeVersionOverride
+      }
     }
   }