Fix run_vm_tests for Windows

runtime/bin/run_vm_tests.cc

Index: runtime/bin/run_vm_tests.cc
diff --git a/runtime/bin/run_vm_tests.cc b/runtime/bin/run_vm_tests.cc
index 3d4ddd3ef7bf1e69c308fac0a19ad11627afc359..0be95651216b44bc6ccfc0731f0bfb1189360e2f 100644
--- a/runtime/bin/run_vm_tests.cc
+++ b/runtime/bin/run_vm_tests.cc
@@ -88,6 +88,7 @@ static int Main(int argc, const char** argv) {
       // List all tests and benchmarks and exit without initializing the VM.
       TestCaseBase::RunAll();
       Benchmark::RunAll(argv[0]);
+      fflush(stdout);
       return 0;
     } else if (strcmp(argv[1], "--benchmarks") == 0) {
       run_filter = kAllBenchmarks;