mkimage limits the length of the file paths in can deal with to 256
characters. Turns out that in automated builds by asu we break this
limit, so increase it to 1024 characters.
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
(cherry picked from commit 3fbf9689b652e230e21bbc7ab2a9b8c936bd6e80)
