Expose CXX_FLAGS through __config__

[robieta]

Stack from ghstack:

• Enable callgrind collection for C++ snippets #47865 Enable callgrind collection for C++ snippets
• Add support for timing C++ snippets. #47864 Add support for timing C++ snippets.
• Rework compat bindings. #47863 Rework compat bindings.
• Add option for cpp_extensions to compile standalone executable #47862 Add option for cpp_extensions to compile standalone executable
• Expose CXX_FLAGS through __config__ #47861 Expose CXX_FLAGS through config

Differential Revision: D25199263

[dr-ci]

💊 CI failures summary and remediations

As of commit 57bfc98 (more details on the Dr. CI page):

---

✅ None of the CI failures appear to be your fault 💚

---

• 1/1 broken upstream at merge base 0213a38 on Nov 30 from 7:48am to 3:47pm PDT (15 commits; 5bb2a87 - d74f2d2)

---

🚧 1 fixed upstream failure:

These were probably caused by upstream breakages that were already fixed.

Please rebase on the viable/strict branch (expand for instructions)

Since your merge base is older than viable/strict, run these commands:

git fetch https://github.com/pytorch/pytorch viable/strict
git rebase FETCH_HEAD

Check out the recency history of this "viable master" tracking branch.

• pytorch_bazel_build on Nov 30 from 7:48am to 3:47pm PDT (15 commits; 5bb2a87 - d74f2d2)
  • 🔁 rerun

---

This comment was automatically generated by Dr. CI (expand for details).

Follow this link to opt-out of these comments for your Pull Requests.

Please report bugs/suggestions on the GitHub issue tracker or post in the (internal) Dr. CI Users group.

See how this bot performed.

This comment has been revised 23 times.

[robieta]

@pytorchbot retest this please

[ezyang]

This error message is not as descriptive as it could be. Why is CXX_FLAGS only for OSS build?

[robieta]

Buck does not populate the `CXX_FLAGS` field of Caffe2 build options. As a result, get_cxx_flags is OSS only.?

[facebook-github-bot]

@robieta merged this pull request in 27905df.