gnu: Add linux-libre 5.19.

gnu: Add linux-libre 5.19.

* gnu/packages/linux.scm (linux-libre-5.19-version,
linux-libre-5.19-gnu-revision, deblob-scripts-5.19,
linux-libre-5.19-pristine-source, linux-libre-5.19-source,
linux-libre-headers-5.19, linux-libre-5.19): New variables.
* gnu/packages/aux-files/linux-libre/5.19-arm.conf,
gnu/packages/aux-files/linux-libre/5.19-arm64.conf,
gnu/packages/aux-files/linux-libre/5.19-i686.conf,
gnu/packages/aux-files/linux-libre/5.19-x86_64.conf: New files.
* Makefile.am (AUX_FILES): Add them.