Squashed 'external/devlib/' changes from 6fe78b4d..9661c6bf

9661c6bf target: Handle non-existing /sys/devices/system/node
0aeb5bc4 target: Remove use of ls
a5640502 devlib/AndroidTarget: Allow passing format options to dump_logcat()

git-subtree-dir: external/devlib
git-subtree-split: 9661c6bff31c5a26a7d3d396550a7d4238eb4856