Expand QTC variables from PathChooser

This would allow to use QTC variables in settings using this widget
such as Extra Debugging Helpers.

Change-Id: I8ac6de46f359f58a501f09774d992a19b48d7d5f
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/libs/utils/pathchooser.h

@@ -39,6 +39,7 @@ QT_END_NAMESPACE
 namespace Utils {
 
 class FancyLineEdit;
+class MacroExpander;
 class Environment;
 class PathChooserPrivate;
 
@@ -135,6 +136,11 @@ public:
     // Enable a history completer with a history of entries.
     void setHistoryCompleter(const QString &historyKey, bool restoreLastItemFromHistory = false);
 
+    // Sets a macro expander that is used when producing path and fileName.
+    // By default, the global expander is used.
+    // nullptr can be passed to disable macro expansion.
+    void setMacroExpander(MacroExpander *macroExpander);
+
     bool isReadOnly() const;
     void setReadOnly(bool b);