spec: own /etc/sysconfig/kernel

`grubby` reads the `/etc/sysconfig/kernel` file which isn't owned by the
package, nor created by it. This leads to all image build tooling having
to take special care to write this file [1] [2] so produced deliverables
automatically update their kernels.

This commit moves the creation of this file to the `grubby` package so
things work 'out of the box' instead of needing to do out-of-package
configuration by third parties.

[1]: https://pagure.io/fedora-kiwi-descriptions/blob/f43/f/root/etc/sysconfig
[2]: a8fafe8d9b/data/distrodefs/fedora/imagetypes.yaml (L1027-L1028)

Signed-off-by: Simon de Vlieger <supakeen@redhat.com>

grubby.spec

@@ -3,7 +3,7 @@
 
 Name: grubby
 Version: 8.40
-Release: 85%{?dist}
+Release: 86%{?dist}
 Summary: Command line tool for updating bootloader configs
 License: GPL-2.0-or-later
 Source1: grubby-bls
@@ -12,6 +12,7 @@ Source3: COPYING
 Source5: 95-kernel-hooks.install
 Source6: 10-devicetree.install
 Source7: grubby.8
+Source8: kernel.sysconfig
 
 BuildRequires: gcc
 BuildRequires: glib2-devel
@@ -59,6 +60,9 @@ install -D -m 0755 -t %{buildroot}%{_prefix}/lib/kernel/install.d/ %{SOURCE6}
 mkdir -p %{buildroot}%{_mandir}/man8
 install -m 0644 %{SOURCE7} %{buildroot}%{_mandir}/man8/
 
+mkdir -p %{buildroot}%{_sysconfdir}/sysconfig
+install -m 0644 %{SOURCE8} %{buildroot}%{_sysconfdir}/sysconfig/kernel
+
 %post
 if [ "$1" = 2 ]; then
     arch=$(uname -m)
@@ -72,8 +76,12 @@ fi
 %attr(0755,root,root) %{_prefix}/lib/kernel/install.d/10-devicetree.install
 %attr(0755,root,root) %{_prefix}/lib/kernel/install.d/95-kernel-hooks.install
 %{_mandir}/man8/grubby.8*
+%config(noreplace) %{_sysconfdir}/sysconfig/kernel
 
 %changelog
+* Wed Dec 10 2025 Simon de Vlieger <cmdr@supakeen.com> - 8.40-86
+- Own `/etc/sysconfig/kernel` which is used for `grubby` configuration
+
 * Wed Jul 30 2025 Leo Sandoval <lsandova@redhat.com> - 8.40-85
 - Update cfg when setting a default kernel
 

kernel.sysconfig

@@ -0,0 +1,6 @@
+# UPDATEDEFAULT specifies if kernel-install should make
+# new kernels the default
+UPDATEDEFAULT=yes
+
+# DEFAULTKERNEL specifies the default kernel package type
+DEFAULTKERNEL=kernel-core