Export proxy and testing at runtime.

Works in the viewer now with a trimmed audio clip.

Diffs=
473dbcb5c Export proxy and testing at runtime. (#6950)

Co-authored-by: Luigi Rosso <luigi-rosso@users.noreply.github.com>

.rive_head

@@ -1 +1 @@
-a69bfba11ec4a116b8712af0b685aa27a5309e43
+473dbcb5ccba6d5cb077f762ac7094ca492d6319

viewer/src/viewer_content/scene_content.cpp

@@ -14,6 +14,8 @@
 #include "rive/math/aabb.hpp"
 #include "rive/assets/image_asset.hpp"
 #include "viewer/viewer_content.hpp"
+#include "rive/relative_local_asset_loader.hpp"
+
 #ifdef RIVE_RENDERER_TESS
 #include "viewer/sample_tools/sample_atlas_packer.hpp"
 #endif
@@ -382,7 +384,9 @@ class SceneContent : public ViewerContent
 std::unique_ptr<ViewerContent> ViewerContent::Scene(const char filename[])
 {
     auto bytes = LoadFile(filename);
-    if (auto file = rive::File::import(bytes, RiveFactory()))
+    rive::RelativeLocalAssetLoader loader(filename);
+    rive::ImportResult result;
+    if (auto file = rive::File::import(bytes, RiveFactory(), &result, &loader))
     {
         return rivestd::make_unique<SceneContent>(filename, std::move(file));
     }