ExtensionManager: Fix qbs build

Amends 6ffe1a8061.

Change-Id: Ibb35fe606f25bd1e1b7a5d457062299f50f80af1
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/extensionmanager/extensionmanager.qbs

@@ -4,6 +4,7 @@ QtcPlugin {
     name: "ExtensionManager"
 
     Depends { name: "Core" }
+    Depends { name: "Spinner" }
     Depends { name: "Tasking" }
     Depends { name: "Qt.network" }