[gnome-sudoku] Fixup for the previous commit

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 672deab72f60d6975b205bc2092457a91288a154
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Mon Jul 11 23:21:18 2016 -0500

    Fixup for the previous commit
    
    once_flag needs to be static or this gets called multiple times....
    
    https://bugzilla.gnome.org/show_bug.cgi?id=768345

 lib/qqwing-wrapper.cpp |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/lib/qqwing-wrapper.cpp b/lib/qqwing-wrapper.cpp
index f659732..188c47f 100644
--- a/lib/qqwing-wrapper.cpp
+++ b/lib/qqwing-wrapper.cpp
@@ -39,7 +39,7 @@ int* qqwing_generate_puzzle(int difficulty)
     const int MAX_ITERATIONS = 1000;
     const int BOARD_SIZE = 81;
     qqwing::SudokuBoard board;
-    std::once_flag flag;
+    static std::once_flag flag;
 
     std::call_once(flag, [] {
         srand(time(nullptr));