rpm-ostree: Setup readonly sysroot for ostree & rw karg

- Enable read only sysroot in the ostree repo config.
- Add `rw` to the kernel arguments to keep statefull parts of the system
  (/var & /etc) writable.

See: https://fedoraproject.org/wiki/Changes/Silverblue_Kinoite_readonly_sysroot
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2086489

pyanaconda/modules/payloads/payload/rpm_ostree/installation.py

@@ -475,6 +475,8 @@ def _set_kargs(self):
         if root_data.type == "btrfs subvolume":
             set_kargs_args.append("rootflags=subvol=" + root_name)
 
+        set_kargs_args.append("rw")
+
         safe_exec_with_redirect("ostree", set_kargs_args, root=self._sysroot)
 
 
@@ -520,6 +522,17 @@ def run(self):
              self._data.remote + ':' + ref]
         )
 
+        log.info("ostree config set sysroot.readonly true")
+
+        safe_exec_with_redirect(
+            "ostree",
+            ["config",
+             "--repo=" + self._physroot + "/ostree/repo",
+             "set",
+             "sysroot.readonly",
+             "true"]
+        )
+
         log.info("ostree admin deploy complete")
         self.report_progress(_("Deployment complete: {}").format(ref))