BUILD: makefile: enable USE_RT on Solaris
It doesn't build on Ultra5 under Solaris 10 without this due to
clock_gettime() not being found.
diff --git a/Makefile b/Makefile
index 785e313..94be6d1 100644
--- a/Makefile
+++ b/Makefile
@@ -332,7 +332,7 @@
# We also enable getaddrinfo() which works since solaris 8.
set_target_defaults = $(call default_opts, \
USE_POLL USE_TPROXY USE_LIBCRYPT USE_CRYPT_H USE_GETADDRINFO USE_THREAD \
- USE_OBSOLETE_LINKER USE_EVPORTS)
+ USE_RT USE_OBSOLETE_LINKER USE_EVPORTS)
TARGET_CFLAGS = -DFD_SETSIZE=65536 -D_REENTRANT -D_XOPEN_SOURCE=500 -D__EXTENSIONS__
TARGET_LDFLAGS = -lnsl -lsocket
endif