chore(ci): support combined akmods-kernel-cache in build

Relates: ublue-os/akmods#295

This is expected to fail until the akmods PR is merged.

Containerfile

@@ -14,7 +14,6 @@ ARG SHA_HEAD_SHORT="${SHA_HEAD_SHORT}"
 ARG VERSION_TAG="${VERSION_TAG}"
 ARG VERSION_PRETTY="${VERSION_PRETTY}"
 
-FROM ghcr.io/ublue-os/${KERNEL_FLAVOR}-kernel:${FEDORA_MAJOR_VERSION}-${KERNEL_VERSION} AS kernel
 FROM ghcr.io/ublue-os/akmods:${KERNEL_FLAVOR}-${FEDORA_MAJOR_VERSION}-${KERNEL_VERSION} AS akmods
 FROM ghcr.io/ublue-os/akmods-extra:${KERNEL_FLAVOR}-${FEDORA_MAJOR_VERSION}-${KERNEL_VERSION} AS akmods-extra
 
@@ -257,7 +256,7 @@ RUN --mount=type=cache,dst=/var/cache/rpm-ostree \
 
 # Install kernel
 RUN --mount=type=cache,dst=/var/cache/rpm-ostree \
-    --mount=type=bind,from=kernel,src=/tmp/rpms,dst=/tmp/kernel-rpms \
+    --mount=type=bind,from=akmods,src=/kernel-rpms,dst=/tmp/kernel-rpms \
     rpm-ostree cliwrap install-to-root / && \
     echo "Will install ${KERNEL_FLAVOR} kernel" && \
     rpm-ostree override replace \