[build] Disable clang-format on generated code

Nice to have, but would make maintain the templates a lot harder.

src/mbgl/style/layers/background_layer.cpp

@@ -1,3 +1,5 @@
+// clang-format off
+
 // This file is generated. Edit scripts/generate-style-code.js, then run `make style-code`.
 
 #include <mbgl/style/layers/background_layer.hpp>
@@ -249,3 +251,5 @@ Mutable<Layer::Impl> BackgroundLayer::mutableBaseImpl() const {
 
 } // namespace style
 } // namespace mbgl
+
+// clang-format on