Add scons-3.1.2

Bug: 1205898
Change-Id: I2d115772b2bb77c6dd5560ca6d293fc132651e41
Reviewed-on: https://chromium-review.googlesource.com/c/native_client/src/third_party/+/3110563
Reviewed-by: Derek Schuff <dschuff@chromium.org>
210 files changed