Update on "gemma3 e2e runner on cuda"

This diff introduces e2e runner for gemma3 model on cuda delegating using AOTI library, which is guarded by CI. Also other necessary infrastructure updates for building and running the `gemma3 e2e runner` on CUDA devices.

Differential Revision: [D85087532](https://our.internmc.facebook.com/intern/diff/D85087532/)

[ghstack-poisoned]

Author: Gasoonjia

extension/tensor/CMakeLists.txt

@@ -24,11 +24,6 @@ target_include_directories(
 )
 target_compile_options(extension_tensor PUBLIC ${_common_compile_options})
 
-# Define USE_CUDA_BACKEND when building with CUDA backend support
-if(EXECUTORCH_BUILD_CUDA)
-  target_compile_definitions(extension_tensor PUBLIC USE_CUDA_BACKEND)
-endif()
-
 # Install libraries
 install(
   TARGETS extension_tensor

extension/tensor/targets.bzl

@@ -10,10 +10,6 @@ def define_common_targets():
     for aten_mode in get_aten_mode_options():
         aten_suffix = ("_aten" if aten_mode else "")
 
-        # Check if USE_CUDA_BACKEND flag is set via build config
-        use_cuda_backend = native.read_config("executorch", "use_cuda_backend", "false") == "true"
-        preprocessor_flags = ["-DUSE_CUDA_BACKEND"] if use_cuda_backend else []
-
         runtime.cxx_library(
             name = "tensor" + aten_suffix,
             srcs = [
@@ -29,7 +25,6 @@ def define_common_targets():
             visibility = [
                 "@EXECUTORCH_CLIENTS",
             ],
-            preprocessor_flags = preprocessor_flags,
             deps = [
                 "//executorch/runtime/core/exec_aten/util:dim_order_util" + aten_suffix,
                 "//executorch/runtime/core/exec_aten/util:tensor_util" + aten_suffix,