python/mkvenv: create timestamp file for each group "ensured"

Each group ensured by the mkvenv script will create an empty timestamp
file named {groupname}.group which can be used to conditionally trigger
dependency installation from various scripts and build machinery.

Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20260218213416.674483-3-jsnow@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>

python/scripts/mkvenv.py

@@ -838,6 +838,12 @@ def ensure_group(
             raise Ouch(result[0])
         raise SystemExit(f"\n{result[0]}\n\n")
 
+    if inside_a_venv():
+        for group in groups:
+            path = Path(sys.prefix).joinpath(f"{group}.group")
+            with open(path, "w", encoding="UTF8"):
+                pass
+
 
 def post_venv_setup() -> None:
     """