New comment by gt7-void on void-packages repository

https://github.com/void-linux/void-packages/pull/23839#issuecomment-664002452

Comment:
> How did it fail when using the Void qwt?

```
In file included from Charts/AllPlot.cpp:20:
Charts/AllPlot.h:26:10: fatal error: qwt_axis_id.h: No such file or directory
   26 | #include <qwt_axis_id.h>
      |          ^~~~~~~~~~~~~~~
compilation terminated.
```
If I remove this `#include` I get warnings like
```
Charts/AllPlot.h:66:7: note: forward declaration of 'class QwtAxisId'
   66 | class QwtAxisId;
```
and errors like
```
  524 |         while(from != to) --to, delete reinterpret_cast<T*>(to->v);
/usr/include/qt5/QtCore/qlist.h:526:61: error: invalid use of incomplete type 'class QwtAxisId'
  526 |         while (from != to) --to, reinterpret_cast<T*>(to)->~T();
```
so it seems to be really necessary.

If you want to have a look, I've pushed gt7-void:GoldenCheetah-qwt with my attempt. Maybe I'm overlooking something.

Thanks for your comments.