Generate header with version #defines for LibTorch (#50073)
Summary:
Uses cmake's `configure_file()` macro to generate a new `torch/csrc/api/include/torch/version.h` header with `TORCH_VERSION_{MAJOR,MINOR,PATCH}` \#defines from an input file `torch/csrc/api/include/torch/version.h.in`.
For Bazel builds, this is accomplished with `header_template_rule()`.
For Buck builds, this is accomplished with `fb_native.genrule()`.
Fixes https://github.com/pytorch/pytorch/issues/44365
<img width="1229" alt="Screen Shot 2021-01-05 at 3 19 24 PM" src="https://user-images.githubusercontent.com/75754324/103809279-3fd80380-5027-11eb-9039-fd23922cebd5.png">
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50073
Reviewed By: glaringlee
Differential Revision: D25855877
Pulled By: jbschlosser
fbshipit-source-id: 6bb792718c97e2c2dbaa74b7b7b831a4f6938e49
