Create shared libs correctly, fix mingw build

Originally committed as revision 18884 to svn://svn.ffmpeg.org/ffmpeg/trunk

subdir.mak

@@ -54,7 +54,7 @@ $(SUBDIR)$(SLIBNAME): $(SUBDIR)$(SLIBNAME_WITH_MAJOR)
 
 $(SUBDIR)$(SLIBNAME_WITH_MAJOR): $(OBJS)
 	$(SLIB_CREATE_DEF_CMD)
-	$(CC) $(SHFLAGS) $(FFLDFLAGS) -o $$@ $$(filter-out $(DEP_LIBS),$$^) $(FFEXTRALIBS) $(EXTRAOBJS)
+	$(CC) $(SHFLAGS) $(FFLDFLAGS) -o $$@ $$(filter %.o,$$^) $(FFEXTRALIBS) $(EXTRAOBJS)
 	$(SLIB_EXTRA_CMD)
 
 ifdef SUBDIR