checkbox-touch: exit build-me if get-libs wasn't run

This patch makes build-me check existance of certain paths related to
requirement libs. If any those directories and/or files are missing, it usually
means that get-libs wasn't run prior to build-me execution.

Fixes: https://bugs.launchpad.net/checkbox-touch/+bug/1394607
Signed-off-by: Maciej Kisielewski <maciej.kisielewski@canonical.com>
"automatic merge of lp:~kissiel/checkbox/fix-1394607/ by tarmac [r=zkrynicki][bug=1394607][author=kissiel]"