NPTL/ARC: fix __lll_lock_wait_private redefinition for static links

Commit 2d9740a65a "uclibc: nptl: fix __lll_lock_wait_private multiple definition"
did a sweeping change which did for all in tree arches at that time (ARC
wasn't)

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

libpthread/nptl/sysdeps/unix/sysv/linux/arc/lowlevellock.c

@@ -24,8 +24,10 @@
 #include <tls.h>
 #include <tcb-offsets.h>
 
-
 void
+#ifndef IS_IN_libpthread
+weak_function
+#endif
 __lll_lock_wait_private (int *futex)
 {
   if (*futex == 2)