stages/rpm: support marking install as ostree

An ostree system can be identified as such by the presence of a
marker file: /run/ostree-booted. The `rpm-ostree` tool also
creates this marker during the _installation_ of the system[1,2].
Recently, starting with F36, the authselect package has taken
has become mandatory[3] and is now owning the nsswitch config.
An rpm-ostree system, which has parts of the user database in
/usr, release on the nss-altfiles to read these databases. The
necessary entries are added during the post-processing, which
is called in our `org.osbuild.ostree.preptree` stage[4]. This
installation is skipped though if the nsswitch is the file is
a symlink, indicating that it is owned by some other package,
like authselect. So the F36 authselect change first broke rpm-
ostree[6]. The fix was to check for `/run/ostree-booted` in
the authselect scriptlet and special case this situation[7,8].
Now, our `org.osbuild.rpm` stage does not yet have the ability
to pretend it is a running ostree system and thus we did not
get the special treatment resulting in nss-altfiles not being
enabled in our ostree commits. Therefore the passwd database in
/usr was not read and a lot of daemons and programs without a
valid user, like e.g. `sshd`.
This change introduces a new option, `ostree_booted` that if
set, will create the `/run/ostree-booted` marker and thus our
installation phase will get the same treatments from packages
as rpm-ostree. Hopefully.

[1] 730bec87b1/rust/src/builtins/compose/mod.rs (L24)
[2] 6211d1452e/src/app/rpmostree-compose-builtin-tree.cxx (L501)
[3] https://fedoraproject.org/wiki/Changes/Make_Authselect_Mandatory
[4] 7993c6f565/rust/src/composepost.rs (L635)
[5] d614caeca1/f/0010-spec-fix-detection-of-ostree-system.patch
[6] https://bugzilla.redhat.com/show_bug.cgi?id=2034360
[7] https://src.fedoraproject.org/rpms/authselect/c/d614caeca1a68f55542aefd0d76bda2691c85d24?branch=f36
[8] https://github.com/authselect/authselect/issues/48

stages/org.osbuild.rpm

@@ -100,6 +100,10 @@ SCHEMA = """
         }
       ]
     }
+  },
+  "ostree_booted": {
+    "type": "boolean",
+    "description": "Create the '/run/ostree-booted' marker"
   }
 }
 """
@@ -143,6 +147,10 @@ SCHEMA_2 = """
        "items": {
         "type": "string"
       }
+    },
+    "ostree_booted": {
+      "type": "boolean",
+      "description": "Create the '/run/ostree-booted' marker"
     }
   }
 },
@@ -160,6 +168,12 @@ SCHEMA_2 = """
 """
 
 
+# File to mark a system as ostree booted. Also used by certain packages
+# like e.g. authselect, to adjust its behavior during installation.
+# Controlled via the `ostree_booted` option.
+OSTREE_BOOTED_MARKER = "run/ostree-booted"
+
+
 def generate_package_metadata(tree):
     query = r"""\{
     "name": "%{NAME}",
@@ -284,6 +298,13 @@ def main(tree, inputs, options):
 
     machine_id_created = create_machine_id_if_needed(tree)
 
+    ostree_booted = None
+    if options.get("ostree_booted", False):
+        os.makedirs(f"{tree}/run", exist_ok=True)
+        ostree_booted = f"{tree}/{OSTREE_BOOTED_MARKER}"
+        with open(ostree_booted, "w", encoding="utf-8") as f:
+            f.write("")
+
     extra_args = []
 
     if options.get("exclude", {}).get("docs"):
@@ -338,6 +359,9 @@ def main(tree, inputs, options):
         machine_id_file.unlink()
         machine_id_file.touch()
 
+    if ostree_booted:
+        os.unlink(ostree_booted)
+
     # remove random seed from the tree if exists
     with contextlib.suppress(FileNotFoundError):
         os.unlink(f"{tree}/var/lib/systemd/random-seed")