MacOS requires c++ flag
Summary:
To install on MacOS, `-stdlib=libc++` needs to be specified.
Pull Request resolved:
@@ -62,7 +62,10 @@ After PyTorch is installed, you can install fairseq with `pip`:
```
pip install fairseq
```
-
+On MacOS,
+```
+CFLAGS="-stdlib=libc++" pip install fairseq
+```
**Installing from source**
To install fairseq from source and develop locally:
