BUILD: enable poll() by default in the makefile
This allows to build haproxy for unknown targets and still have poll().
If for any reason a target does not support it, just passing USE_POLL=""
disables it.
diff --git a/Makefile b/Makefile
index daa64ee..da6efe9 100644
--- a/Makefile
+++ b/Makefile
@@ -192,7 +192,10 @@
# Depending on the target platform, some options are set, as well as some
# CFLAGS and LDFLAGS. The USE_* values are set to "implicit" so that they are
# not reported in the build options string. You should not have to change
-# anything there.
+# anything there. poll() is always supported, unless explicitly disabled by
+# passing USE_POLL="" on the make command line.
+USE_POLL = default
+
ifeq ($(TARGET),generic)
# generic system target has nothing specific
USE_POLL = implicit