The checked-in file is two lines saying the real content is generated by cmake.
It is: `cmake/Codegen.cmake:47` writes it to `${CMAKE_BINARY_DIR}`, `build.bzl:16`
to the Bazel output tree, and only the generated one is installed.

Nothing includes the placeholder. `caffe2/core/common.h` asks for the full path
`"caffe2/core/macros.h"`, so the quoted-include search of its own directory looks
for `caffe2/core/caffe2/core/macros.h` and misses; the `-I` search then finds the
build tree, listed ahead of the source tree.

Authored with an AI assistant.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/194230
Approved by: https://github.com/janeyx99