spec: Add dnf-bootc subpackage

dnf-bootc's only job is to Require python3-gobject-base, ostree,
ostree-libs, and util-linux-core, which are needed to interact with
bootc systems. We don't want to add these dependencies on `python3-dnf`
because we don't want them on non-bootc systems, so we use a subpackage.

dnf.spec

@@ -190,6 +190,17 @@ Requires:       python3-%{name} = %{version}-%{release}
 %description automatic
 Systemd units that can periodically download package upgrades and apply them.
 
+%package bootc
+Summary:        %{pkg_summary} - additional bootc dependencies
+Requires:       python3-%{name} = %{version}-%{release}
+Requires:       ostree
+Requires:       ostree-libs
+Requires:       python3-gobject-base
+Requires:       util-linux-core
+
+%description bootc
+Additional dependencies needed to perform transactions on booted bootc (bootable containers) systems.
+
 
 %prep
 %autosetup
@@ -420,6 +431,9 @@ popd
 %{python3_sitelib}/%{name}/automatic/
 %endif
 
+%files bootc
+# bootc subpackage does not include any files
+
 %changelog
 * Tue Nov 12 2024 Evan Goode <mail@evangoo.de> - 4.22.0-1
 - doc: Naming of source and debug repos