build: mov_muxer requires ac3_parser

Reviewed-by: Benoit Fouet <benoit.fouet@free.fr>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

configure

@@ -2413,7 +2413,7 @@ matroska_muxer_select="riffenc"
 mmf_muxer_select="riffenc"
 mov_demuxer_select="riffdec"
 mov_demuxer_suggest="zlib"
-mov_muxer_select="riffenc rtpenc_chain"
+mov_muxer_select="riffenc rtpenc_chain ac3_parser"
 mp3_demuxer_select="mpegaudio_parser"
 mp4_muxer_select="mov_muxer"
 mpegts_muxer_select="adts_muxer latm_muxer"