Set our own QQC style at startup

Summary:
Set the QtQuickControls style to our own: for QtQuickControls1
it will fall back to Desktop, while it will use our own org.kde.desktop
for QtQuickControlsStyle and Kirigami

Test Plan: systemsettings redesign uses qstyle qqc style, for both qqc1 and 2

Reviewers: #plasma, davidedmundson

Reviewed By: #plasma, davidedmundson

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D5720

startkde/startkde.cmake

@@ -94,6 +94,10 @@ fi
 #otherwise apps that manually opt in for high DPI get auto scaled by the developer AND manually scaled by us
 export QT_AUTO_SCREEN_SCALE_FACTOR=0
 
+#Set the QtQuickControls style to our own: for QtQuickControls1
+#it will fall back to Desktop, while it will use our own org.kde.desktop
+#for QtQuickControlsStyle and Kirigami
+export QT_QUICK_CONTROLS_STYLE=org.kde.desktop
 
 # XCursor mouse theme needs to be applied here to work even for kded or ksmserver
 if test -n "$kcminputrc_mouse_cursortheme" -o -n "$kcminputrc_mouse_cursorsize" ; then

startkde/startplasma.cmake

@@ -49,6 +49,11 @@ if test -z "$dl"; then
   esac
 fi
 
+#Set the QtQuickControls style to our own: for QtQuickControls1
+#it will fall back to Desktop, while it will use our own org.kde.desktop
+#for QtQuickControlsStyle and Kirigami
+export QT_QUICK_CONTROLS_STYLE=org.kde.desktop
+
 # Activate the kde font directories.
 #
 # There are 4 directories that may be used for supplying fonts for KDE.