libebur128: 1.0.2 -> 1.2.4

Semi-automatic update. These checks were performed:

- built on NixOS
- found 1.2.4 with grep in /nix/store/m2zvs6x1g15cz7gbf97wdn89gw7swwal-libebur128-1.2.4
- found 1.2.4 in filename of file in /nix/store/m2zvs6x1g15cz7gbf97wdn89gw7swwal-libebur128-1.2.4

cc "@andrewrk"