lavf/Makefile: Fix kux demuxer standalone compilation.

libavformat/Makefile

@@ -276,6 +276,7 @@ OBJS-$(CONFIG_IVR_DEMUXER)               += rmdec.o rm.o rmsipr.o
 OBJS-$(CONFIG_JACOSUB_DEMUXER)           += jacosubdec.o subtitles.o
 OBJS-$(CONFIG_JACOSUB_MUXER)             += jacosubenc.o rawenc.o
 OBJS-$(CONFIG_JV_DEMUXER)                += jvdec.o
+OBJS-$(CONFIG_KUX_DEMUXER)               += flvdec.o
 OBJS-$(CONFIG_LATM_MUXER)                += latmenc.o rawenc.o
 OBJS-$(CONFIG_LMLM4_DEMUXER)             += lmlm4.o
 OBJS-$(CONFIG_LOAS_DEMUXER)              += loasdec.o rawdec.o