add suggestion to use lld to CONTRIBUTING.md (#21334)

suo · facebook-github-bot · commit ca3256399973 · 2019-06-04T15:40:49.000-07:00
Summary: I found this significantly speeds up incremental builds. Pull Request resolved: #21334 Differential Revision: D15632994 Pulled By: suo fbshipit-source-id: bb4af90f4400bffa90d168d82ff30fece5e3835c
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
@@ -349,6 +349,16 @@ ccache -F 0
 # deploy (and add to ~/.bashrc for later)
 export PATH="/usr/lib/ccache:$PATH"
 ```
+#### Use a faster linker
+If you are editing a single file and rebuilding in a tight loop, the time spent 
+linking will dominate. The system linker available in most Linux distributions 
+(GNU `ld`) is quite slow. Use a faster linker, like [lld](https://lld.llvm.org/).
+
+The easiest way to use `lld` this is download the 
+[latest LLVM binaries](http://releases.llvm.org/download.html#8.0.0) and run:
+```
+ln -s /path/to/downloaded/ld.lld /usr/local/bin/ld
+```
 
 ## CUDA Development tips
 
