Revert 239102 "Move build/build_config_functions.h to sandbox/"

> Move build/build_config_functions.h to sandbox/
> 
> There is not much support for build/build_config_functions.h,
> as highlighted in http://goo.gl/3ufXOJ. Move it away.
> 
> R=jww@chromium.org
> 
> Review URL: https://codereview.chromium.org/106163008

TBR=jln@chromium.org

Review URL: https://codereview.chromium.org/107643002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239105 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 239105