IP_RECVERR is not defined on Mac (#899)
IP_RECVERR is not defined on Mac (#899)

Summary:
Problem:
- `IP_RECVERR` symbol is not defined on Mac OS.
- A test expects this symbol to be found. But, in the case on Mac OS, the symbol is not found and hence will cause a hard compiler error.

Solution:
- `ifdef` the portion of the test that is relying on this symbol.
Pull Request resolved: https://github.com/facebook/folly/pull/899

Differential Revision: D9140373

Pulled By: yfeldblum

fbshipit-source-id: 127ab352cea790194171376ac809c23249883251

facebook/folly,facebook/folly,facebook/folly,facebook/folly,facebook/folly