LU-1617 build: ignore automatically generated files

Do not list automatically generated files in "git status" output,
so that it does not hide checkpatch.pl output in the commit message.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: Iab5c5be25de7dc54225fb2aa6540a4d75e500c1e
Reviewed-on: http://review.whamcloud.com/6229


Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: John Hammond <johnlockwoodhammond@gmail.com>
Reviewed-by: Keith Mannthey <keith.mannthey@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>