Update instructions in building_for_linux.md (#20)

Summary:
According to issue #19, the package `libxcb-glx0-dev` is required for some OpenGL headers needed by the X windowing system.

Pull Request resolved: #20

Reviewed By: leapally

Differential Revision: D59733651

Pulled By: enpe

fbshipit-source-id: 314f56778304246289139ef32ff8d8f49b3afdff

building_for_linux.md

@@ -15,7 +15,7 @@ This document describes the process to build Ocean on Linux.
       xz-devel
 
   # Ubuntu
-  sudo apt-get install libx11-dev libudev-dev liblzma-dev libgl1-mesa-dev
+  sudo apt-get install libx11-dev libudev-dev liblzma-dev libgl1-mesa-dev libxcb-glx0-dev
   ```
 
 ## 2 Building the third-party libraries