Error loading shared library librav1e.so.0

Building on master, I get the error Error loading shared library librav1e.so.0.
This seems oddly similar to #13 but the opposite way around, looking for librav1e.so.0 rather than librav1e.so

`$ docker run -it ffmpeg ffmpeg -encoders
Error loading shared library librav1e.so.0: No such file or directory (needed by /opt/ffmpeg/bin/ffmpeg)
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_data_unref: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_context_new: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_frame_new: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_config_set_time_base: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_frame_fill_plane: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_send_frame: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_status_to_str: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_config_default: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_config_set_color_description: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_config_parse_int: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_config_parse: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_config_unref: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_receive_packet: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_twopass_out: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_context_unref: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_frame_unref: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_frame_set_opaque: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_packet_unref: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_twopass_in: symbol not found
Error relocating /opt/ffmpeg/bin/ffmpeg: rav1e_config_set_pixel_format: symbol not found`