Add new c9s-rt variant

I think having an image with RT enabled out of the box just makes
sense.

oscore/bootc.yaml

@@ -1,7 +1,7 @@
 # A relatively minimal base, but we also do include linux-firmware so
 # we can be directly booted on metal.
 packages:
- - kernel systemd
+ - systemd
  # linux-firmware now a recommends so let's explicitly include it
  # https://gitlab.com/cki-project/kernel-ark/-/commit/32271d0cd9bd52d386eb35497c4876a8f041f70b
  # https://src.fedoraproject.org/rpms/kernel/c/f55c3e9ed8605ff28cb9a922efbab1055947e213?branch=rawhide

oscore/kernel-rt.yaml

@@ -0,0 +1,10 @@
+repos:
+  - rt
+  - nfv
+
+# Enable the "realtime" AKA soft-realtime AKA latency-optimized kernel.
+packages:
+ - kernel-rt-core kernel-rt-modules kernel-rt-modules-extra kernel-rt-kvm
+
+exclude-packages:
+  - kernel-rt-debug-core

oscore/kernel.yaml

@@ -0,0 +1,6 @@
+# Enable the Linux kernel; see also kernel-rt.
+packages:
+ - kernel
+
+exclude-packages:
+  - kernel-debug