VcsManager: Fix adding files to VCS from locator

The files are listed by file name without path, so git add was executed
from the user's working directory instead of the target directory.

Amends commit 48c56416f5.

Change-Id: Iba7c5ff33378265d3c22479d7abb6ccf8db75d07
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: André Hartmann <aha_1980@gmx.de>

src/plugins/coreplugin/vcsmanager.cpp

@@ -445,7 +445,7 @@ void VcsManager::promptToAdd(const QString &directory, const QStringList &fileNa
     if (dlg.exec() == QDialog::Accepted) {
         QStringList notAddedToVc;
         foreach (const QString &file, unmanagedFiles) {
-            if (!vc->vcsAdd(file))
+            if (!vc->vcsAdd(QDir(directory).filePath(file)))
                 notAddedToVc << file;
         }