checkpatch output in shippable log displays without line breaks

[dbkinder]

The checkpatch output shown in the shippable log shows up as one l-o-n-g line making it hard to read.
See, for example, https://app.shippable.com/github/zephyrproject-rtos/zephyr/runs/4432/3/tests

[nashif]

yes, already reported

[pfalcon]

+1