checkasm/Makefile: add EXTRALIBS-swresample

Should fix https://ffmpeg.org/pipermail/ffmpeg-devel/2018-February/225058.htmlSigned-off-by: Muhammad Faiz <mfcc64@gmail.com>

tests/checkasm/Makefile

@@ -61,7 +61,7 @@ tests/checkasm/checkasm.o: CFLAGS += -Umain
 CHECKASM := tests/checkasm/checkasm$(EXESUF)
 
 $(CHECKASM): $(CHECKASMOBJS) $(FF_STATIC_DEP_LIBS)
-	$(LD) $(LDFLAGS) $(LDEXEFLAGS) $(LD_O) $(CHECKASMOBJS) $(FF_STATIC_DEP_LIBS) $(EXTRALIBS-avcodec) $(EXTRALIBS-avfilter) $(EXTRALIBS-avutil) $(EXTRALIBS)
+	$(LD) $(LDFLAGS) $(LDEXEFLAGS) $(LD_O) $(CHECKASMOBJS) $(FF_STATIC_DEP_LIBS) $(EXTRALIBS-avcodec) $(EXTRALIBS-avfilter) $(EXTRALIBS-avutil) $(EXTRALIBS-swresample) $(EXTRALIBS)
 
 checkasm: $(CHECKASM)