Drop build host kernel version

[bmwiedemann]

This caused variations in build results
when building in a chroot or container on hosts with different
Linux kernel versions.

For openSUSE Tumbleweed we also update the kernel often,
but do not want to publish new oyranos binaries that
did not differ otherwise.

See also https://reproducible-builds.org/ for why this matters.

This PR was done while working on reproducible builds for openSUSE.

Diff was thus:

/usr/lib64/libOyranosCore.so.0.9.6 differs in ELF section .rodata
@@ -145,7 +145,7 @@
  138c0 65200a20 0a200a20 0a200a43 4d414b45  e . . . . .CMAKE
  138d0 5f535953 54454d5f 4e414d45 3a204c69  _SYSTEM_NAME: Li
  138e0 6e757820 0a434d41 4b455f53 59535445  nux .CMAKE_SYSTE
- 138f0 4d3a204c 696e7578 2d342e32 302e342d  M: Linux-4.20.4-
+ 138f0 4d3a204c 696e7578 2d342e32 302e362d  M: Linux-4.20.6-
  13900 312d6465 6661756c 74200a43 4d414b45  1-default .CMAKE
  13910 5f535953 54454d5f 50524f43 4553534f  _SYSTEM_PROCESSO
  13920 523a2078 38365f36 34200a0a 48415645  R: x86_64 ..HAVE

[beku]

Highly appreciated. Thanks :-)