Detect if we run as flatpak

Fixes #9110

gajim/common/app.py

@@ -157,7 +157,7 @@ _dependencies = {
     'GSPELL': False,
     'IDLE': False,
     'RUN_AS_FLATPAK': False,
-    }
+}
 
 
 def is_installed(dependency):
@@ -296,6 +296,10 @@ def detect_dependencies():
     except (ImportError, ValueError):
         pass
 
+    # RUN AS FLATPAK
+    if os.path.exists('/app/share/run-as-flatpak'):
+        _dependencies['RUN_AS_FLATPAK'] = True
+
     # Print results
     for dep, val in _dependencies.items():
         log('gajim').info('%-13s %s', dep, val)