docs: update the link to the horizontal whitespace rule

docs/mac_build_instructions.md

 # Mac Build Instructions
 
 [TOC]
 
 ## Prerequisites
 
 *   A Mac running 10.9+.
 *   https://developer.apple.com/xcode, 5+
 *   Install
     [gclient](http://dev.chromium.org/developers/how-tos/install-depot-tools),
@@ skipping 93 matching lines @@
 When these tests are built, you will find them in the `out/{Debug|Release}`
 directory. You can run them from the command line:
 
     ~/chromium/src/out/Release/unit_tests
 
 
 ## Coding
 
 According to the
 [Chromium style guide](http://dev.chromium.org/developers/coding-style) code is
-[not allowed to have whitespace on the ends of lines](http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml#Horizontal_Whitespace).
+[not allowed to have whitespace on the ends of lines](https://google.github.io/styleguide/cppguide.html#Horizontal_Whitespace).
 If you edit in Xcode, know that it loves adding whitespace to the ends of lines
 which can make editing in Xcode more painful than it should be. The
 [GTM Xcode Plugin](http://code.google.com/p/google-toolbox-for-mac/downloads/list)
 adds a preference panel to Xcode that allows you to strip whitespace off of the
 ends of lines on save. Documentation on how to install it is
 [here](http://code.google.com/p/google-toolbox-for-mac/wiki/GTMXcodePlugin).
 
 ## Debugging
 
 Good debugging tips can be found
@@ skipping 102 matching lines @@
 be set in `/etc/sysctl.conf`:
 
     echo kern.maxvnodes=$((512*1024)) | sudo tee -a /etc/sysctl.conf
 
 Or edit the file directly.
 
 If your `git --version` reports 2.6 or higher, the following may also improve
 performance of `git status`:
 
     git update-index --untracked-cache