another attempt to fix signed/unsigned comparison warning in OS X build

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@61316 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

utils/screenshotgen/src/autocapture.cpp

@@ -61,7 +61,7 @@ void AutoCaptureMechanism::Delay(int seconds)
 
     // Wait for 3 seconds
     clock_t start = clock();
-    while ( (long)clock() - start < CLOCKS_PER_SEC * seconds)
+    while ( clock() - start < (clock_t)CLOCKS_PER_SEC * seconds)
         wxYieldIfNeeded();
 }