Build fail on ubuntu 18.04 about openr

[cooperlees]

Hi Sir,

This is known (and is why CI is failing). Just haven’t got a fix as internally we have this header file (not sure why it’s not Open Source yet).

We feel here we should do something similar to the way folly has a configure file that generates a cpp header (only way to get the macro into the translation unit). This allows you to have arbitrary CMake logic to define or unset a macro and ultimately have a #define VAR or #undef VAR:
Configure_file docs: https://cmake.org/cmake/help/latest/command/configure_file.html

We should be able to build without using Folly’s exception_tracer.

[guodong]

Thanks for your reply @cooperlees ! I also found a pull request from folly, facebook/folly#1484
I'll give a try now.