message: Update build instructions link
diff: @@ -9,7 +9,7 @@ menu: main
  - [Materials Overview]
  - [Materials Ref Sheet]
  -[Build Instructions]: https://github.com/google/filament/blob/master/README.md
  +[Build Instructions]: https://github.com/google/filament/blob/main/BUILDING.md
  [Filament Design]: https://google.github.io/filament/Filament.html
  [Materials Overview]: https://google.github.io/filament/Materials.html
  [Materials Ref Sheet]: https://google.github.io/filament/Material%20Properties.pdf
  