treewide: add meta.mainProgram to audio

pkgs/applications/audio/cadence/default.nix

···
     license = lib.licenses.gpl2Plus;
     maintainers = with lib.maintainers; [ ];
     platforms = [ "x86_64-linux" ];
+    mainProgram = "cadence";
   };
 }

pkgs/applications/audio/cava/default.nix

···
     license = licenses.mit;
     maintainers = with maintainers; [ offline mirrexagon ];
     platforms = platforms.linux;
+    mainProgram = "cava";
   };
 }

pkgs/applications/audio/easyeffects/default.nix

···
     license = licenses.gpl3Plus;
     maintainers = with maintainers; [ ];
     platforms = platforms.linux;
+    mainProgram = "easyeffects";
   };
 }

pkgs/applications/audio/helvum/default.nix

···
     license = licenses.gpl3Only;
     maintainers = with maintainers; [ fufexan ];
     platforms = platforms.linux;
+    mainProgram = "helvum";
   };
 }

pkgs/applications/audio/lollypop/default.nix

···
     license = licenses.gpl3Plus;
     maintainers = with maintainers; [ lovesegfault ];
     platforms = platforms.linux;
+    mainProgram = "lollypop";
   };
 }

pkgs/applications/audio/mpdevil/default.nix

···
     license = licenses.gpl3Plus;
     platforms = platforms.linux;
     maintainers = with maintainers; [ apfelkuchen6 ];
+    mainProgram = "mpdevil";
   };
 }

pkgs/applications/audio/ncmpcpp/default.nix

···
     license     = licenses.gpl2Plus;
     maintainers = with maintainers; [ jfrankenau koral lovek323 ];
     platforms   = platforms.all;
+    mainProgram = "ncmpcpp";
   };
 }

pkgs/applications/audio/pavucontrol/default.nix

···
 
     maintainers = with maintainers; [ abbradar globin ];
     platforms = platforms.linux;
+    mainProgram = "pavucontrol";
   };
 }

pkgs/applications/audio/spotify/default.nix

···
     sourceProvenance = with sourceTypes; [ binaryNativeCode ];
     license = licenses.unfree;
     platforms = [ "x86_64-linux" "x86_64-darwin" "aarch64-darwin" ];
+    mainProgram = "spotify";
   };
 
 in if stdenv.isDarwin

pkgs/applications/audio/strawberry/default.nix

···
     maintainers = with maintainers; [ peterhoeg ];
     # upstream says darwin should work but they lack maintainers as of 0.6.6
     platforms = platforms.linux;
+    mainProgram = "strawberry";
   };
 }

pkgs/applications/audio/tageditor/default.nix

···
     license = licenses.gpl2;
     maintainers = [ maintainers.matthiasbeyer ];
     platforms = platforms.linux;
+    mainProgram = "tageditor";
   };
 }

pkgs/applications/audio/youtube-music/default.nix

···
     sourceProvenance = with sourceTypes; [ binaryNativeCode ];
     platforms = platforms.linux;
     maintainers = [ maintainers.aacebedo ];
+    mainProgram = "youtube-music";
   };
 }

pkgs/applications/audio/ytmdesktop/default.nix

···
     license = licenses.cc0;
     platforms = platforms.linux;
     maintainers = [ maintainers.lgcl ];
+    mainProgram = "ytmdesktop";
   };
 }