Support XPU ABI=0 build (#130110)

# Motivation
This PR intends to support ABI=0 build for XPU backend.

# Additional Context
The major change is adding a compilation option `-D__INTEL_PREVIEW_BREAKING_CHANGES` for the host compiler(gcc) and `-fpreview-breaking-changes` for XPU device kernel code compiler(icpx), why?
Because we use
- gcc to compile host code and link SYCL runtime. So we need to pass `-D__INTEL_PREVIEW_BREAKING_CHANGES` to tell the host compiler invoking the ABI-neutral API included in SYCL. And
- use icpx to compile device kernel code and link SYCL runtime. So we need to pass `-fpreview-breaking-changes` to tell the device kernel compiler building ABI-neutral code. Besides,
- `libsycl-preview.so` is an ABI-neutral library but `libsycl.so` is not.

This PR depends on https://github.com/pytorch/pytorch/pull/131643.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/130110
Approved by: https://github.com/EikanWang, https://github.com/gujinghui, https://github.com/albanD

README.md

@@ -252,6 +252,8 @@ If you would like to compile PyTorch with [new C++ ABI](https://gcc.gnu.org/onli
 export _GLIBCXX_USE_CXX11_ABI=1
 ```
 
+Please **note** that starting from PyTorch 2.5, the PyTorch build with XPU supports both new and old C++ ABIs. Previously, XPU only supported the new C++ ABI. If you want to compile with Intel GPU support, please follow [Intel GPU Support](#intel-gpu-support).
+
 If you're compiling for AMD ROCm then first run this command:
 ```bash
 # Only run this if you're compiling for ROCm

cmake/Dependencies.cmake

@@ -90,6 +90,10 @@ if(USE_XPU)
     message(WARNING "Not compiling with XPU. Could NOT find SYCL."
     "Suppress this warning with -DUSE_XPU=OFF.")
     caffe2_update_option(USE_XPU OFF)
+  else()
+    if(LINUX)
+      string(APPEND CMAKE_CXX_FLAGS " -D__INTEL_PREVIEW_BREAKING_CHANGES")
+    endif()
   endif()
 endif()
 

cmake/Modules/FindMKLDNN.cmake

@@ -42,12 +42,16 @@ IF(NOT MKLDNN_FOUND)
         list(APPEND DNNL_MAKE_COMMAND "--" "-l" "$ENV{MAX_JOBS}")
       endif()
     endif()
+    if(LINUX)
+      set(ABI_NEUTRAL_FLAGS -fpreview-breaking-changes)
+    endif()
     ExternalProject_Add(xpu_mkldnn_proj
       SOURCE_DIR ${MKLDNN_ROOT}
       PREFIX ${XPU_MKLDNN_DIR_PREFIX}
       BUILD_IN_SOURCE 0
       CMAKE_ARGS  -DCMAKE_C_COMPILER=icx
       -DCMAKE_CXX_COMPILER=${SYCL_CXX_DRIVER}
+      -DCMAKE_CXX_FLAGS=${ABI_NEUTRAL_FLAGS}
       -DDNNL_GPU_RUNTIME=SYCL
       -DDNNL_CPU_RUNTIME=THREADPOOL
       -DDNNL_BUILD_TESTS=OFF

cmake/Modules/FindSYCLToolkit.cmake

@@ -51,7 +51,7 @@ find_file(
 # Find SYCL library fullname.
 find_library(
   SYCL_LIBRARY
-  NAMES sycl
+  NAMES sycl-preview
   HINTS ${SYCL_LIBRARY_DIR}
   NO_DEFAULT_PATH
 )