Cleanup: Use CLOG instead of printf for USD logging

These printfs were missed from the previous change 7bb78be256.

Same rationale as before for unifying these traces under the CLOG
infrastructure.

Pull Request: https://projects.blender.org/blender/blender/pulls/117777

source/blender/io/usd/intern/usd_blend_shape_utils.cc

@@ -223,8 +223,9 @@ void create_blend_shapes(pxr::UsdStageRefPtr stage,
   pxr::UsdSkelBindingAPI skel_api = pxr::UsdSkelBindingAPI::Apply(mesh_prim);
 
   if (!skel_api) {
-    printf("WARNING: couldn't apply UsdSkelBindingAPI to prim %s\n",
-           mesh_prim.GetPath().GetAsString().c_str());
+    CLOG_WARN(&LOG,
+              "Couldn't apply UsdSkelBindingAPI to mesh prim %s",
+              mesh_prim.GetPath().GetAsString().c_str());
     return;
   }
 

source/blender/io/usd/intern/usd_writer_abstract.cc

@@ -15,6 +15,9 @@
 
 #include "DNA_mesh_types.h"
 
+#include "CLG_log.h"
+static CLG_LogRef LOG = {"io.usd"};
+
 /* TfToken objects are not cheap to construct, so we do it once. */
 namespace usdtokens {
 /* Materials */
@@ -140,7 +143,9 @@ bool USDAbstractWriter::mark_as_instance(const HierarchyContext &context, const
   BLI_assert(context.is_instance());
 
   if (context.export_path == context.original_export_path) {
-    printf("USD ref error: export path is reference path: %s\n", context.export_path.c_str());
+    CLOG_ERROR(&LOG,
+               "Reference error: export path matches reference path: %s",
+               context.export_path.c_str());
     BLI_assert_msg(0, "USD reference error");
     return false;
   }
@@ -150,9 +155,10 @@ bool USDAbstractWriter::mark_as_instance(const HierarchyContext &context, const
     /* See this URL for a description for why referencing may fail"
      * https://graphics.pixar.com/usd/docs/api/class_usd_references.html#Usd_Failing_References
      */
-    printf("USD Export warning: unable to add reference from %s to %s, not instancing object\n",
-           context.export_path.c_str(),
-           context.original_export_path.c_str());
+    CLOG_WARN(&LOG,
+              "Unable to add reference from %s to %s, not instancing object for export",
+              context.export_path.c_str(),
+              context.original_export_path.c_str());
     return false;
   }