Download protobuf dependency on ARM64 build host

[qc-tbhardwa]

Windows on ARM support AMD64 emulation, so we can use win64 version of protoc.

Description
Compilation on ARM64 machine fails due to missing protoc dependency.

Motivation and Context
With this change we can compile onnxruntime on Windows on Arm devices without setting protobuf manually. CMake will download and setup protoc dependency.

[HectorSVC]

/azp run Linux QNN CI Pipeline,Win_TRT_Minimal_CUDA_Test_CI,Windows ARM64 QNN CI Pipeline,Windows GPU Doc Gen CI Pipeline,Windows x64 QNN CI Pipeline

[azure-pipelines]

Azure Pipelines successfully started running 5 pipeline(s).

[HectorSVC]

We have built on ARM64 machine for a long time, never encounter any issue with protoc. Don't know what's the issue you you encountered.

[qc-tbhardwa]

If we try to compile arm64ec on arm64 device then it fails with below error.

Doing crosscompiling
Numpy version: 2.2.5
-- Loading Dependencies URLs ...
-- Loading Dependencies ...
-- Abseil source dir:C:/repos/onnxruntime_gqa/build/arm64_build_err_ec/Release/_deps/abseil_cpp-src
-- CMAKE_HOST_SYSTEM_NAME: Windows
CMake Error at external/onnxruntime_external_deps.cmake:162 (message):
ONNX_CUSTOM_PROTOC_EXECUTABLE must be set to cross-compile.
Call Stack (most recent call first):
CMakeLists.txt:699 (include)

For cross-compiling, we are not fetching protoc if processor is AM64.