Backport export of lzma_mt_block_size symbol.

This restores binary compatibility against liblzma 5.6.0 library.

PR: 278127

(cherry picked from commit 5ffb19ac36c4b5c9e72d69048250c8e56acff739)

Revert "MFV: xz 5.6.0"

This commit reverts 8db56defa766eacdbaf89a37f25b11a57fd9787a,
rolling back the vendor import of xz 5.6.0 and restoring the
package to version 5.4.5.

The revert was not direct

Revert "MFV: xz 5.6.0"

This commit reverts 8db56defa766eacdbaf89a37f25b11a57fd9787a,
rolling back the vendor import of xz 5.6.0 and restoring the
package to version 5.4.5.

The revert was not directly due to the attack (CVE-2024-3094):
our import process have removed the test cases and build scripts
that would have enabled the attack. However, reverting would
help to reduce potential confusion and false positives from
security scanners that assess risk based solely on version
numbers.

Another commit will follow to restore binary compatibility with
the liblzma 5.6.0 library by making the previously private
symbol (lzma_mt_block_size) public.

PR: 278127

(cherry picked from commit 2f9cd13d6c1824633251fb4267c9752d3b044a45)

show more ...

MFC: liblzma: don't export lzma_lz_decoder_uncompressed

It was removed in the 5.4.0 import.

(cherry picked from commit 023fa553bf0000837738ce3ba118921ee24e3792)

MFV: xz 5.6.0.

(cherry picked from commit 8db56defa766eacdbaf89a37f25b11a57fd9787a)