Debugger: Fix compile

Amends b6d3e67270.

Change-Id: I0acf8a7bb447e99f7bccfc8f5055a49163727619
Reviewed-by: Artem Sokolovskii <artem.sokolovskii@qt.io>
Reviewed-by: hjk <hjk@qt.io>

src/plugins/debugger/gdb/gdbengine.cpp

@@ -1613,6 +1613,7 @@ QString GdbEngine::cleanupFullName(const QString &fileName)
                         QString path = filePath.path();
                         m_baseNameToFullName.insert(name, path);
                     }
+                    return true;
                 },
                 {"*"},
                 QDir::NoFilter,