[test] Fix mkdir on unix in dawg test.
[test] Fix mkdir on unix in dawg test.

tesseract-ocr/tesseract,tesseract-ocr/tesseract,stweil/tesseract,UB-Mannheim/tesseract,UB-Mannheim/tesseract,amitdo/tesseract,tesseract-ocr/tesseract,tesseract-ocr/tesseract,amitdo/tesseract,tesseract-ocr/tesseract,stweil/tesseract,amitdo/tesseract,stweil/tesseract,amitdo/tesseract,stweil/tesseract,UB-Mannheim/tesseract,UB-Mannheim/tesseract,stweil/tesseract,amitdo/tesseract,UB-Mannheim/tesseract