Add "-lrt" in Makefile for Solaris.

This fix is from @NanXiao, however I was not able to retain authorship
because the Pull Request original repository was removed.

src/Makefile

@@ -58,7 +58,7 @@ ifeq ($(uname_S),SunOS)
 	# SunOS
 	INSTALL=cp -pf
 	FINAL_CFLAGS+= -D__EXTENSIONS__ -D_XPG6
-	FINAL_LIBS+= -ldl -lnsl -lsocket -lresolv -lpthread
+	FINAL_LIBS+= -ldl -lnsl -lsocket -lresolv -lpthread -lrt
 else
 ifeq ($(uname_S),Darwin)
 	# Darwin (nothing to do)