Incompatible with system-installed RtAudio 6.x

[OPNA2608]

Same issue with OPN2BankEditor.

-- Checking for module 'rtaudio'
--   Found rtaudio, version 6.0.1
[...]
In file included from /build/source/src/bank_editor.h:30,
                 from /build/source/src/audio.cpp:19:
/build/source/src/audio/ao_rtaudio.h:37:31: error: 'RtAudioError' has not been declared
   37 |     static void errorCallback(RtAudioError::Type type, const std::string &errorText);
      |                               ^~~~~~~~~~~~
/build/source/src/audio/ao_rtaudio.h:37:50: error: expected ',' or '...' before 'type'
   37 |     static void errorCallback(RtAudioError::Type type, const std::string &errorText);
      |                                                  ^~~~

With version 6.0.0, RtAudio switched its error reporting method from C++ exceptions to return values.

An example for how this was addressed in BambooTracker, via a hard switch to RtAudio 6.x: BambooTracker/BambooTracker@cac4786.

[Wohlstand]

Try the latest version from the git, I already switched some, or wait, that's I did with AdlRt, I'll try to check some soon.