QmlProject: Fix import paths for code model

This fixes a regression introduced by
30638df441.

Custom import paths have to be absolute for the code model.

Change-Id: I232229fa58c3900fe684ca4529b2ed08bf93e8be
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

src/plugins/qmlprojectmanager/qmlproject.h

@@ -75,6 +75,7 @@ public:
 
     void refreshProjectFile();
 
+    static QStringList makeAbsolute(const Utils::FileName &path, const QStringList &relativePaths);
 protected:
     RestoreResult fromMap(const QVariantMap &map, QString *errorMessage) override;
     bool setupTarget(ProjectExplorer::Target *t) override;