[#100] RPM spec fixes

[kolyshkin]

Bring the spec file to the working state:

1. Replace chrpath with cmake option -DCMAKE_SKIP_RPATH=true to fix
   all the check-rpaths warnings.

2. Fix a build failure caused by missing mkdir.

3. Fix a typo in ncurses-lib package name.

While at it, fix/simplify rpm build instructions in doc/RPM.md.

[jesperpedersen]

@kolyshkin Could you add yourself to https://github.com/HighResMusicPlayer/hrmp/blob/main/doc/DEVELOPERS.md#authors and squash the commits ? Thanks !

[jesperpedersen]

Please, do [#100] RPM spec fixes as the commit message

[kolyshkin]

Commits squashed; commit/PR title and description updated.

Could you add yourself to https://github.com/HighResMusicPlayer/hrmp/blob/main/doc/DEVELOPERS.md#authors

I do not consider myself an author, I'm merely a minor contributor fixing the issue I came across. If there would be a "contributors" list, I can add myself to it.

[jesperpedersen]

@kolyshkin It is a contribution that adds value, so I think you should add yourself to the authors. But, it is your choice of course

[jesperpedersen]

@kolyshkin Maybe you can integrate something like, pgagroal/pgagroal@ae6c369

[kolyshkin]

@kolyshkin Maybe you can integrate something like, pgagroal/pgagroal@ae6c369

Can certainly do that, but that's a separate task. This PR merely fixes the non-working rpm build.

Will take a closer look tomorrow if time permits.

[jesperpedersen]

Rebased, and merged.

Thanks for your contribution !

[jesperpedersen]

@kolyshkin Hopefully you can contribute addional improvements for the RPM build chain