McuSupport: Expand variables for automatic kits

An MCU kit that is created automatically also requires variable
expansion before the kit is generated. The same preparation for
the variables will be done as the MCU option page.

Task-number: UL-6603
Change-Id: I915f6f6e8c6e2a90409c527951e469c555002cff
Reviewed-by: Rainer Keller <Rainer.Keller@qt.io>
Reviewed-by: Yasser Grimes <yasser.grimes@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/mcusupport/mcusupportoptions.h

@@ -40,6 +40,7 @@ public:
     Targets mcuTargets;
     Packages packages;
 
+    static void updateQtDirMacro(const Utils::FilePath &qulDir);
     void expandVariablesAndWildcards();
     MacroExpanderPtr getMacroExpander(const McuTarget &target);