Due to the test on the target introduced by commit
9577a152b ("BUILD:
makefile: do not erase build options for some build options"), if a
tool (e.g. halog) is build first before haproxy after a clean or a
fresh source extraction, the .build_opts file does not exist and
"make" complains since there's no such target. Make sure to define
the empty target for all "else" blocks there. No backport is needed.
else
.build_opts:
endif # ignore_opts
+else
+.build_opts:
endif # non-empty target
haproxy: $(OPTIONS_OBJS) $(OBJS)