libavformat/Makefile: Fix build issues with async test

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/Makefile

@@ -547,11 +547,11 @@ SLIBOBJS-$(HAVE_GNU_WINDRES)             += avformatres.o
 SKIPHEADERS-$(CONFIG_FFRTMPCRYPT_PROTOCOL) += rtmpdh.h
 SKIPHEADERS-$(CONFIG_NETWORK)            += network.h rtsp.h
 
-TESTPROGS = async                                                       \
-            seek                                                        \
+TESTPROGS = seek                                                        \
             srtp                                                        \
             url                                                         \
 
+TESTPROGS-$(CONFIG_ASYNC_PROTOCOL)       += async
 TESTPROGS-$(CONFIG_NETWORK)              += noproxy
 TESTPROGS-$(CONFIG_FFRTMPCRYPT_PROTOCOL) += rtmpdh