Support linux aarch64 for Dart and Flutter (#2342)

Adds support for building and packaging Linux AArch64 (arm64) artifacts alongside x64 for Dart/Flutter plugins.

- Detects host architecture in CMake and adjusts library paths
- Extends test workflows to run on an ARM runner and handle linux-aarch64 paths
- Splits release pipeline into separate x64 and aarch64 build/package jobs

flutter/sherpa_onnx_linux/linux/CMakeLists.txt

@@ -7,11 +7,19 @@ cmake_minimum_required(VERSION 3.10)
 set(PROJECT_NAME "sherpa_onnx_linux")
 project(${PROJECT_NAME} LANGUAGES CXX)
 
+if(CMAKE_SYSTEM_PROCESSOR STREQUAL "x86_64")
+  set(LIB_ARCH_DIR "x64")
+elseif(CMAKE_SYSTEM_PROCESSOR STREQUAL "aarch64")
+  set(LIB_ARCH_DIR "aarch64")
+else()
+  message(FATAL_ERROR "Unsupported arch: ${CMAKE_SYSTEM_PROCESSOR}")
+endif()
+
 # List of absolute paths to libraries that should be bundled with the plugin.
 # This list could contain prebuilt libraries, or libraries created by an
 # external build triggered from this build file.
 set(sherpa_onnx_linux_bundled_libraries
-  "${CMAKE_CURRENT_SOURCE_DIR}/libsherpa-onnx-c-api.so"
-  "${CMAKE_CURRENT_SOURCE_DIR}/libonnxruntime.so"
+  "${CMAKE_CURRENT_SOURCE_DIR}/${LIB_ARCH_DIR}/libsherpa-onnx-c-api.so"
+  "${CMAKE_CURRENT_SOURCE_DIR}/${LIB_ARCH_DIR}/libonnxruntime.so"
   PARENT_SCOPE
 )