cmake: allow build on Raspbian GNU/Linux 9 (stretch)
cmake: allow build on Raspbian GNU/Linux 9 (stretch)

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