runtime: initialize the variable

gcc thinks this could be uninitialized; make it so.

src/util/runtime.c

@@ -110,7 +110,7 @@ GIT_INLINE(int) init_unlock(void)
 
 int git_runtime_init(git_runtime_init_fn init_fns[], size_t cnt)
 {
-	int ret;
+	int ret = 0;
 
 	if (init_lock() < 0)
 		return -1;