syscalls/futex: Fix compilation.

I've mistaken LDFLAGS and LDLIBS again, sorry everyone (fixes build in OBS).

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
diff --git a/testcases/kernel/syscalls/futex/Makefile b/testcases/kernel/syscalls/futex/Makefile
index feda8db..61b5cfe 100644
--- a/testcases/kernel/syscalls/futex/Makefile
+++ b/testcases/kernel/syscalls/futex/Makefile
@@ -18,8 +18,8 @@
 
 top_srcdir		?= ../../../..
 
-futex_wait02: LDFLAGS+=-lrt
-futex_wake03: LDFLAGS+=-lrt
+futex_wait02: LDLIBS+=-lrt
+futex_wake03: LDLIBS+=-lrt
 futex_wait03: CFLAGS+=-pthread
 futex_wake02: CFLAGS+=-pthread