git: fix unpackaged python files

git: fix unpackaged python files

* EXTRA_OEMAKE is needed after inheriting autotools which sets it to empty
* fixes:
git-1.7.7: git: Files/directories were installed but not shipped
  /usr/lib64
  /usr/lib64/python2.7
  /usr/lib64/python2.7/site-packages
  /usr/lib64/python2.7/site-packages/git_remote_helpers-0.1.0-py2.7.egg-info
  /usr/lib64/python2.7/site-packages/git_remote_helpers
  /usr/lib64/python2.7/site-packages/git_remote_helpers/__init__.py
  /usr/lib64/python2.7/site-packages/git_remote_helpers/util.pyc
  /usr/lib64/python2.7/site-packages/git_remote_helpers/__init__.pyc
  /usr/lib64/python2.7/site-packages/git_remote_helpers/util.py
  /usr/lib64/python2.7/site-packages/git_remote_helpers/git
  /usr/lib64/python2.7/site-packages/git_remote_helpers/git/__init__.py
  /usr/lib64/python2.7/site-packages/git_remote_helpers/git/importer.pyc
  /usr/lib64/python2.7/site-packages/git_remote_helpers/git/non_local.pyc
  /usr/lib64/python2.7/site-packages/git_remote_helpers/git/exporter.py
  /usr/lib64/python2.7/site-packages/git_remote_helpers/git/git.py
  /usr/lib64/python2.7/site-packages/git_remote_helpers/git/repo.py
  /usr/lib64/python2.7/site-packages/git_remote_helpers/git/__init__.pyc
  /usr/lib64/python2.7/site-packages/git_remote_helpers/git/importer.py
  /usr/lib64/python2.7/site-packages/git_remote_helpers/git/exporter.pyc
  /usr/lib64/python2.7/site-packages/git_remote_helpers/git/repo.pyc
  /usr/lib64/python2.7/site-packages/git_remote_helpers/git/git.pyc
  /usr/lib64/python2.7/site-packages/git_remote_helpers/git/non_local.py

* fixes [YOCTO #3344]

(From OE-Core rev: 8231e9d455c71fe1bd3c4776985ff775c6af3f6d)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>