removesilence: Add $(LIBM) to libraries
/usr/bin/ld: .libs/libgstremovesilence_la-vad_private.o: in function vad_set_threshold': ./gst/removesilence/vad_private.c:108: undefined reference to
pow'
/usr/bin/ld: .libs/libgstremovesilence_la-vad_private.o: in function vad_get_threshold_as_db': ./gst/removesilence/vad_private.c:114: undefined reference to
log10'