qt: Remove left-over partial files more persistently
* lang/qt/src/Makefile.am: Add new files. * lang/qt/src/cleaner.cpp, lang/qt/src/cleaner.h: New. * lang/qt/src/util.cpp (PartialFileGuard::~PartialFileGuard): Call Cleaner::removeFile instead of removeFile. * lang/qt/src/util.cpp, lang/qt/src/util.h (removeFile): Remove.
If the initial attempt to remove the file fails then a Cleaner is
created that tries to remove the file at regular intervals (10 s)
and on destruction (which happens on application shutdown).
- GnuPG-bug-id: T6584