index-pack: fix compilation with NO_PTHREADS

type_cas_lock/unlock() should be defined as no-op for NO_PTHREADS
build, just like all the other locking primitives.
Signed-off-by: NEtienne Buira <etienne.buira@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin/index-pack.c

@@ -185,6 +185,9 @@ static void cleanup_thread(void)
 #define deepest_delta_lock()
 #define deepest_delta_unlock()
 
+#define type_cas_lock()
+#define type_cas_unlock()
+
 #endif