test: Add tools to search path
test: Add tools to search path

Add tools to makefile's header search path.

Change-Id: Ibd9d560b02c31aa3a25b5ecf52cb6671933051e2
Signed-off-by: Patrick Venture <36c53fa43f47f3fd67cb2fc38031827244d18a1f@google.com>

openbmc/phosphor-ipmi-flash