Adapt indicator-application check for sandboxed environments

Fix quality loss in the tray icon image

Fix window showing by clicking on the tray icon on macOS

Fix tray icon displaying on KDE

docs/building-cmake.md

@@ -235,10 +235,11 @@ Go to ***BuildPath*** and run
 
     git clone git://code.qt.io/qt/qt5.git qt_5_12_5
     cd qt_5_12_5
-    perl init-repository --module-subset=qtbase,qtimageformats
+    perl init-repository --module-subset=qtbase,qtimageformats,qtsvg
     git checkout v5.12.5
     git submodule update qtbase
     git submodule update qtimageformats
+    git submodule update qtsvg
     cd qtbase
     git apply ../../patches/qtbase_5_12_5.diff
     cd src/plugins/platforminputcontexts