update gitignore for more artifacts
update gitignore for more artifacts

Add more autotools artifacts to gitignore file.

Change-Id: Ib935e247a7acba3eedd4c1f7b2bad30bbe04134f
Signed-off-by: Patrick Venture <36c53fa43f47f3fd67cb2fc38031827244d18a1f@google.com>

openbmc/phosphor-ipmi-flash