sp_midi build error on linux

[asmodehn]

I tried this both on stable and on dev, so maybe there is something wrong with my setup... by here is what I got

Scanning dependencies of target sp_midi
[ 89%] Creating directories for 'sp_midi'
[ 90%] No download step for 'sp_midi'
[ 92%] No update step for 'sp_midi'
[ 93%] No patch step for 'sp_midi'
[ 95%] Performing configure step for 'sp_midi'
-- The C compiler identification is GNU 11.2.0
-- The CXX compiler identification is GNU 11.2.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found ALSA: /usr/lib/x86_64-linux-gnu/libasound.so (found version "1.2.4") 
-- Configuring done
-- Generating done
-- Build files have been written to: /home/alexv/Projects/sonic-pi/app/external/build/sp_midi-prefix/src/sp_midi-build
[ 96%] Performing build step for 'sp_midi'
Scanning dependencies of target libsp_midi
[ 14%] Building CXX object CMakeFiles/libsp_midi.dir/src/sp_midi.cpp.o
In file included from /home/alexv/Projects/sonic-pi/app/external/sp_midi/src/hotplug_thread.h:27,
                 from /home/alexv/Projects/sonic-pi/app/external/sp_midi/src/sp_midi.cpp:28:
/home/alexv/Projects/sonic-pi/app/external/sp_midi/src/midiin.h:27:10: fatal error: rtmidi/RtMidi.h: No such file or directory
   27 | #include <rtmidi/RtMidi.h>
      |          ^~~~~~~~~~~~~~~~~
compilation terminated.
gmake[5]: *** [CMakeFiles/libsp_midi.dir/build.make:85: CMakeFiles/libsp_midi.dir/src/sp_midi.cpp.o] Error 1
gmake[4]: *** [CMakeFiles/Makefile2:98: CMakeFiles/libsp_midi.dir/all] Error 2
gmake[3]: *** [Makefile:106: all] Error 2
gmake[2]: *** [CMakeFiles/sp_midi.dir/build.make:130: sp_midi-prefix/src/sp_midi-stamp/sp_midi-build] Error 2
gmake[1]: *** [CMakeFiles/Makefile2:329: CMakeFiles/sp_midi.dir/all] Error 2
gmake: *** [Makefile:103: all] Error 2

My Cmake/C++ is a but rusty, but it seems to me that this is related to external_libs/ not being added to the include_directories in the UNIX case here
It is however included in the source there

Let me know if I can be of any assistance to confirm and/or fix this.
Cheers !

[ethancrawford]

Related: #2542

[samaaron]

We have improved our build process - especially for Linux - in addition to a complete overhaul of how we boot the system.
Therefore, please feel free to re-open if this is still an issue with the recently released v4 of Sonic Pi - https://github.com/sonic-pi-net/sonic-pi/releases