Context: By default, Courgette's writes its log to courgette.log.  This behavior is usually okay, but if we run multiple Courgette instances for testing purposes,  then I/O contention might occur!  This change makes it easier to test Courgette (without creating separate work directories).

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4acd08fa3248e35509ae7e4897d5aab69e2e109d

commit 4acd08fa3248e35509ae7e4897d5aab69e2e109d
Author: Calder Kitagawa <ckitagawa@google.com>
Date: Thu Jan 11 20:16:57 2018

[Courgette]: Added "-nologfile" switch to disable logging to file.

This is a very simple fix if "-nologfile" is present in the command
line args the log file is not created. The logs are still recorded to
stdout.

Bug:  801274 
Change-Id: Iea027ced63b4c0f276859a22ba8adfa3d2579d39
Reviewed-on: https://chromium-review.googlesource.com/862244
Commit-Queue: Calder Kitagawa <ckitagawa@google.com>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#528729}
[modify] https://crrev.com/4acd08fa3248e35509ae7e4897d5aab69e2e109d/courgette/courgette_tool.cc