tessdata: uncompress tarball only once to speed up builds

tessdata: uncompress tarball only once to speed up builds

The previous approach was to uncompress N times a big tarball (638 MB)
where N=130 is the number of supported languages.  Each iteration would
only extract a single file, but it still needs to uncompress the whole
tarball.  This is of course completely inefficient.

Now, we uncompress the tarball only once to extract all relevant files,
and then iterate N times to copy the file needed for each language.

This massively speeds up builds, at the expense of temporarily requiring
more build space (about 1 GB more)

Signed-off-by: Baptiste Jonglez <git@bitsofnetworks.org>