lavf/Makefile: Fix standalone build of AVS2 muxer

Found-by: Paul B Mahol <onemda@gmail.com>

libavformat/Makefile

@@ -115,6 +115,7 @@ OBJS-$(CONFIG_AVI_MUXER)                 += avienc.o mpegtsenc.o avlanguage.o ra
 OBJS-$(CONFIG_AVM2_MUXER)                += swfenc.o swf.o
 OBJS-$(CONFIG_AVR_DEMUXER)               += avr.o pcm.o
 OBJS-$(CONFIG_AVS_DEMUXER)               += avs.o voc_packet.o vocdec.o voc.o
+OBJS-$(CONFIG_AVS2_MUXER)                += rawenc.o
 OBJS-$(CONFIG_BETHSOFTVID_DEMUXER)       += bethsoftvid.o
 OBJS-$(CONFIG_BFI_DEMUXER)               += bfi.o
 OBJS-$(CONFIG_BINK_DEMUXER)              += bink.o