Bug#1051556: soapyaudio: FTBFS with RtAudio 6

[IOhannes m zmoelnig <umlaeute@debian.org>]

Source: soapyaudio
Version: 0.1.1-5
Severity: important
Tags: ftbfs

Dear Maintainer,

soapyaudio ftbfs with RtAudio 6 (currently available in experimental):

```
[ 66%] Building CXX object CMakeFiles/audioSupport.dir/Streaming.cpp.o
/usr/lib/ccache/c++ -DUSE_HAMLIB -D_REENTRANT -D__LINUX_ALSA__ -D__LINUX_PULSE__ -D__UNIX_JACK__ -DaudioSupport_EXPORTS -I/<<PKGBUILDDIR>> -I/usr/include/rtaudio -g -O2 -ffile-prefix-map=/<<PKGBUILDDIR>>=. -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -Wdate-time -D_FORTIFY_SOURCE=2 -std=c++11 -fPIC -fvisibility=hidden -fvisibility-inlines-hidden   -Wno-unused-parameter -pthread -Wall -Wextra -Wnon-virtual-dtor -MD -MT CMakeFiles/audioSupport.dir/Streaming.cpp.o -MF CMakeFiles/audioSupport.dir/Streaming.cpp.o.d -o CMakeFiles/audioSupport.dir/Streaming.cpp.o -c /<<PKGBUILDDIR>>/Streaming.cpp
/<<PKGBUILDDIR>>/Streaming.cpp: In member function ‘virtual int SoapyAudio::activateStream(SoapySDR::Stream*, int, long long int, size_t)’:
/<<PKGBUILDDIR>>/Streaming.cpp:242:14: error: ‘RtAudioError’ does not name a type; did you mean ‘RtAudioErrorType’?
  242 |     } catch (RtAudioError& e) {
      |              ^~~~~~~~~~~~
      |              RtAudioErrorType
/<<PKGBUILDDIR>>/Streaming.cpp:243:59: error: ‘e’ was not declared in this scope
  243 |         throw std::runtime_error("RtAudio init error '" + e.getMessage());
      |                                                           ^
make[3]: *** [CMakeFiles/audioSupport.dir/build.make:107: CMakeFiles/audioSupport.dir/Streaming.cpp.o] Error 1
make[3]: *** Waiting for unfinished jobs....
/<<PKGBUILDDIR>>/Settings.cpp: In member function ‘virtual void SoapyAudio::writeSetting(const std::string&, const std::string&)’:
/<<PKGBUILDDIR>>/Settings.cpp:497:40: warning: catching polymorphic type ‘class std::invalid_argument’ by value [-Wcatch-value=]
  497 |         } catch (std::invalid_argument e) { }
      |                                        ^
make[3]: Leaving directory '/<<PKGBUILDDIR>>/obj-x86_64-linux-gnu'
```

cheers