kernel: predefine KBUILD_BUILD_USER and KBUILD_BUILD_HOST
By exporting KBUILD_BUILD_USER with a pre-defined value we improve the
reproducibility of the kernel and remove the requirement for whoami in the
HOSTTOOLS.
KBUILD_BUILD_HOST also helps improve the reproducibility of the kernel.
For more kernel reproducibility options see:
https://lwn.net/Articles/437864/
Signed-off-by: Joshua Lock <joshua.g.lock@intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
