Check external.mk is ignored only when in the root path of a
br2-external.
Add a file called external.mk as a fixture to be used by the test case.
Signed-off-by: Ricardo Martincoski <ricardo.martincoski@gmail.com>
Cc: Arnout Vandecappelle <arnout@mind.be>
[Arnout: wrap at 80 columns]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
