macOS: Bundle fluidsynth and ghostscript (#3250)

* macOS: Build fixes for fluidsynth and ghostscript to ensure they get detected and bundled. Add required packages for build.

* macOS: Don't link against fluidsynth and only bundle if detected.

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Co-authored-by: cold-brewed <cold-brewed@users.noreply.github.com>

src/sound/CMakeLists.txt

@@ -85,6 +85,12 @@ if(RTMIDI)
 endif()
 
 if(FLUIDSYNTH)
+    if(APPLE)
+        find_library(FLUIDSYNTH_LIB fluidsynth)
+        if (NOT FLUIDSYNTH_LIB)
+            message(WARNING "Could not find fluid synth. The library will not be bundled and any related features will not work.")
+        endif()
+    endif ()
     target_compile_definitions(snd PRIVATE USE_FLUIDSYNTH)
     target_sources(snd PRIVATE midi_fluidsynth.c)
 endif()