redhat/kernel.spec.template: update compression variables to support zstd

Upstream Status: RHEL Only

The kernel.spec.template file has a compression variable to define which binary is used to compress the kernel modules. The binary is currently invoked in the following manner: '%compression -c9'. There is a desire to use zstd for automotive since it results in faster decompression, and faster boot times. To support zstd, different flags need to be passed to the compression binary, so let's introduce a compression_flags variable.

The BuildRequires needs to be updated to include the compression binary as well since these variables can be overridden on the command line with "rpmbuild --define 'compression zstd' ...".

The zstd support was tested with the following configuration:

%global compression zstd
%global compression_flags --rm
%global compext zst

Signed-off-by: Brian Masney bmasney@redhat.com