This is done by copying any training to the temporary tesseract
directory, and always using that as the TESSDIR. This works as
it's writeable (unlike the /app/share directory that flatpak
would otherwise work)
- compile all dependencies from scratch
- don't explicitly set GOOS and GOARCH so a flatpak builder can cross-compile properly
- switch from embedding compiled dependencies to having the wrapper script specify where the relevant things can be found
