build C++ extensions on windows with /std:c++17 (pytorch#97413)

build C++ extensions on windows with /std:c++17

Summary:
We added -std=c++17 to Posix builds, but neglected to add this for
Windows. This just brings back parity.

Test Plan: Rely on CI.

Reviewers: ezyang

Subscribers:

Tasks:

Tags:

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* pytorch#97175
* __->__ pytorch#97413
Pull Request resolved: pytorch#97413
Approved by: https://github.com/ezyang

torch/utils/cpp_extension.py

@@ -1996,7 +1996,7 @@ def _write_ninja_file_to_build_library(path,
     common_cflags += ['-D_GLIBCXX_USE_CXX11_ABI=' + str(int(torch._C._GLIBCXX_USE_CXX11_ABI))]
 
     if IS_WINDOWS:
-        cflags = common_cflags + COMMON_MSVC_FLAGS + extra_cflags
+        cflags = common_cflags + COMMON_MSVC_FLAGS + ['/std:c++17'] + extra_cflags
         cflags = _nt_quote_args(cflags)
     else:
         cflags = common_cflags + ['-fPIC', '-std=c++17'] + extra_cflags