library.mak: Workaround SDL redefining main and breaking fate tests on mingw

Fixes Ticket3368

Commit message by commiter
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

library.mak

@@ -34,6 +34,7 @@ $(SUBDIR)x86/%.o: $(SUBDIR)x86/%$(YASMD).asm
 LIBOBJS := $(OBJS) $(SUBDIR)%.h.o $(TESTOBJS)
 $(LIBOBJS) $(LIBOBJS:.o=.s) $(LIBOBJS:.o=.i):   CPPFLAGS += -DHAVE_AV_CONFIG_H
 $(TESTOBJS) $(TESTOBJS:.o=.i): CPPFLAGS += -DTEST
+$(TESTOBJS) $(TESTOBJS:.o=.i): CFLAGS += -Umain
 
 $(SUBDIR)$(LIBNAME): $(OBJS)
 	$(RM) $@