litert: Enable GPU Accelerator on Android

- Added build target for libLiteRtGpuAccelerator.so

PiperOrigin-RevId: 732300108

Author: terryheo

tensorflow/lite/experimental/litert/cc/BUILD

@@ -459,7 +459,7 @@ cc_test(
 #         "@com_google_absl//absl/log:absl_log",
 #         "@com_google_absl//absl/strings:string_view",
 #         "@com_google_absl//absl/types:span",
-#         "//third_party/odml/infra/ml_drift_delegate:ml_drift_cl_accelerator",  # buildcleaner: keep
+#         "//third_party/odml/infra/ml_drift_delegate/litert:ml_drift_cl_accelerator",  # buildcleaner: keep
 #         "//tensorflow/lite:framework",
 #         "//tensorflow/lite/c:c_api_opaque",
 #         "//tensorflow/lite/c:common",

tensorflow/lite/experimental/litert/core/environment.cc

@@ -14,6 +14,8 @@
 
 #include "tensorflow/lite/experimental/litert/core/environment.h"
 
+#include <dlfcn.h>
+
 #include <memory>
 #include <string>
 #include <utility>
@@ -43,7 +45,12 @@ litert::Expected<LiteRtEnvironmentT::Ptr> LiteRtEnvironmentT::CreateWithOptions(
   }
 
   // Find `LiteRtRegisterAcceleratorGpuOpenCl` to register the GPU delegate.
-  void* lib_opencl = nullptr;
+  static void* lib_opencl =
+      tflite::SharedLibrary::LoadLibrary("libLiteRtGpuAccelerator.so");
+  if (!lib_opencl) {
+    // If the library is not found, find the symbol in the current library.
+    lib_opencl = RTLD_DEFAULT;
+  }
   auto opencl_registrar_func = reinterpret_cast<void (*)(LiteRtEnvironment)>(
       tflite::SharedLibrary::GetLibrarySymbol(
           lib_opencl, "LiteRtRegisterAcceleratorGpuOpenCl"));