Update CONTRIBUTING.md (#3203)
At some point recently we started putting a JSON file in the out/ directory and this broke this suggested build script.
This patch makes the script more resilient to such files.
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 47dc205..6a8912a 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -160,7 +160,7 @@
flutter/tools/gn --android --runtime-mode=release
cd out
-ls | xargs -n 1 sh -c 'ninja -C $0 || exit 255'
+find . -mindepth 1 -maxdepth 1 -type d | xargs -n 1 sh -c 'ninja -C $0 || exit 255'
flutter update-packages --upgrade
```