[atk] Visual Studio 201x builds: Fix previous commit

[Chun-wei Fan <fanchunwei src gnome org>]

commit e309cf84af1675ce0df7e970b4db28bef2d03394
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Tue Jan 10 18:43:03 2017 +0800

    Visual Studio 201x builds: Fix previous commit
    
    The previous commit which moved the project files from build/win32/ to
    win32/ also attempted to clean up things a bit.  This fixes the cleanup.

 win32/vs10/atk-gen-src.props |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/win32/vs10/atk-gen-src.props b/win32/vs10/atk-gen-src.props
index 06bec83..6abbcdc 100644
--- a/win32/vs10/atk-gen-src.props
+++ b/win32/vs10/atk-gen-src.props
@@ -4,7 +4,7 @@
     <Import Project="atk-build-defines.props" />
   </ImportGroup>
   <PropertyGroup Label="UserMacros">
-    <GenConfigH>if exist ..\..\config.h copy ..\..\config.h.win32 ..\..\config.h</GenConfigH>
+    <GenConfigH>if not exist ..\..\config.h copy ..\..\config.h.win32 ..\..\config.h</GenConfigH>
     <GenMarshalSrc>
 cd ..\..\atk