When creating ostree commits, only one kernel package can be installed at a
time, otherwise creating the commit will fail in rpm-ostree. This prevents
ostree type builds (RHEL for Edge and Fedora IoT) to add alternative kernels,
in particular, the real-time kernel (kernel-rt).
Blueprints now support defining the name of the kernel to be used in an image,
through the customizations.kernel.name key. If not specified, the default
kernel package is included as before.
Relevant PRs: #1175