Flush output after every benchmark.

This purely cosmetic change simply allows to see the output of the benchmarks
sooner which is more user-friendly when running several long benchmarks.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65570 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

tests/benchmarks/bench.cpp

@@ -294,6 +294,8 @@ int BenchApp::OnRun()
             wxPrintf("%.2f avg (min=%ld, max=%ld)\n",
                      (float)timeTotal / times, timeMin, timeMax);
         }
+
+        fflush(stdout);
     }
 
     return rc;