Merge pull request #1361 from ppluciennik/ppluciennik/flush_log

Flush changes into .ninja_log right away.
diff --git a/src/build_log.cc b/src/build_log.cc
index 648617c..c75be95 100644
--- a/src/build_log.cc
+++ b/src/build_log.cc
@@ -167,6 +167,9 @@
     if (log_file_) {
       if (!WriteEntry(log_file_, *log_entry))
         return false;
+      if (fflush(log_file_) != 0) {
+          return false;
+      }
     }
   }
   return true;