Fix handling of async IO from pipes on Windows

runtime/bin/process_test.cc

Index: runtime/bin/process_test.cc
diff --git a/runtime/bin/process_test.cc b/runtime/bin/process_test.cc
index e9b09b20ce8a6b9d172a0c49a6d718a4c07c4d2e..578189445b2756477ede989335e68213a8fe8bb8 100644
--- a/runtime/bin/process_test.cc
+++ b/runtime/bin/process_test.cc
@@ -38,11 +38,15 @@ int main(int argc, char* argv[]) {
          (fgets(line, kLineSize, stdin) != NULL)) {
     if (outstream == 0) {
       fprintf(stdout, "%s", line);
+      fflush(stdout);
     } else if (outstream == 1) {
       fprintf(stderr, "%s", line);
+      fflush(stderr);
     } else if (outstream == 2) {
       fprintf(stdout, "%s", line);
       fprintf(stderr, "%s", line);
+      fflush(stdout);
+      fflush(stderr);
     }
     echo_counter++;
   }
@@ -52,6 +56,5 @@ int main(int argc, char* argv[]) {
     *segfault = 1;
   }
 
-
   return exit_code;
 }