cmake: enable link-time optimization by default
cmake: enable link-time optimization by default

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