Document the hacks to build training tools on mac

[giri-kum]

---

Environment

• Tesseract Version: 5.1.0
• Platform: Mac

Current Behavior:

The documentation here https://tesseract-ocr.github.io/tessdoc/tess4/TrainingTesseract-4.00.html#hardware-software-requirements says that

"At time of writing, training only works on Linux. (macOS almost works; it requires minor hacks to the shell scripts to account for the older version of bash it provides and differences in mktemp.)"

Expected Behavior:

It would be beneficial for macOS users to document these minor hacks to help them build the training tools on mac.

Suggested Fix:

Document the hacks to build training tools on mac

[stweil]

This is not a technical problem of Tesseract, but a documentation issue. Therefore I transferred it to tessdoc.

[Shreeshrii]

it requires minor hacks to the shell scripts to account for the older version of bash it provides and differences in mktemp.)"

The comments relate to tesstrain.sh which has already been deprecated in favor of makefile based training.