add xz-utils package

[d1sgr4c3]

hello, @a13xp0p0v !
i have litlle PR
first i got this error

      CALL    /home/vyashnikov/src/scripts/checksyscalls.sh      CHK     include/generated/compile.h
      UPD     include/generated/compile.h      CC      init/version.o
      AR      init/built-in.a      CHK     kernel/kheaders_data.tar.xz
      GEN     kernel/kheaders_data.tar.xz    /bin/sh: 1: xz: not found
    tar: kernel/kheaders_data.tar.xz: Cannot write: Broken pipe    tar: Child returned status 127
    tar: Error is not recoverable: exiting now    make[2]: *** [/home/vyashnikov/src/kernel/Makefile:150: kernel/kheaders_data.tar.xz] Error 2
    ...

i also checked this util in dockerfile and container and didnt found xz

[a13xp0p0v]

Cool, thank you @flipthewho.
Merged.