Pack the darwin build based on the architecture

The current prebuilts put the darwin builds under "darwin/x86_64", so reproduce that behavior for the CMake packaging logic.

PiperOrigin-RevId: 291844613

Author: a-maurice

cmake/cpp_pack.cmake

@@ -44,10 +44,14 @@ if(${FIREBASE_CPP_BUILD_PACKAGE})
   elseif(MSVC)
     set(FIREBASE_LIB_CONFIG_PATH "windows")
   elseif(APPLE)
-    set(FIREBASE_LIB_CONFIG_PATH "darwin")
+    # Use the provided architecture, or fallback to a reasonable default.
+    if(${CMAKE_OSX_ARCHITECTURES} STREQUAL "")
+      set(FIREBASE_LIB_CONFIG_PATH "darwin/x86_64")
+    else()
+      set(FIREBASE_LIB_CONFIG_PATH "darwin/${CMAKE_OSX_ARCHITECTURES}")
+    endif()
   else()
     # Check if building for 32 bit
-    message(STATUS "CMAKE_CXX_FLAGS: ${CMAKE_CXX_FLAGS}")
     if("${CMAKE_CXX_FLAGS}" MATCHES "-m32")
       set(FIREBASE_LIB_CONFIG_PATH "linux/i386")
     else()