lz4 module no longer works

[keith-zephyr]

Describe the bug

PR #93383 made lz4 an optional/external module.

However, the glue logic used by Zephyr applications previously declared in-tree under modules/lz4/CmakeLists.txt and Kconfig wasn't moved into the external module.

This has broken downstream users that were using the lz4 module.

Regression

• This is a regression.

Steps to reproduce

No response

Relevant log output

Impact

Major – Severely degrades functionality; workaround is difficult or unavailable.

Environment

No response

Additional Context

No response

[nashif]

zephyrproject-rtos/lz4#4