Fixes #7925. a) change CWD during split reduced to splitting only. b) fixed...

Fixes #7925. a) change CWD during split reduced to splitting only. b) fixed problem in mkDirParent() with absolute paths, c) make logger independent of CWD, d) fixed problem with `mktemp --tmpdir`(difference Ubuntu 16 / 18) by using PHP function, e) fixed some 'undefined index' problems
1 job for CwdLoggerProblem in 2 minutes and 22 seconds (queued for 13 seconds)