And since this is a change in the gn repository (which we always clone at the latest commit at the time of publishing the tarball), just fixing bootstrap.py is not enough, as M71 and M70 builds would still be affected.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4849d9a19f700961e2c25b642bdaaa6514040e60

commit 4849d9a19f700961e2c25b642bdaaa6514040e60
Author: Raphael Kubo da Costa <raphael.kubo.da.costa@intel.com>
Date: Tue Nov 13 15:41:11 2018

gn bootstrap: Remove sysroot-related options

https://gn-review.googlesource.com/c/gn/+/3200 removed the --no-sysroot
option from gen.py and moved to only use a sysroot in the GN bots, so the
options here no longer have any effect.

Bug:  904350 
Change-Id: Ieddc71a4f8f802c2d050de1c69ca3a9ec788ee88
Reviewed-on: https://chromium-review.googlesource.com/c/1333391
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Raphael Kubo da Costa <raphael.kubo.da.costa@intel.com>
Cr-Commit-Position: refs/heads/master@{#607596}
[modify] https://crrev.com/4849d9a19f700961e2c25b642bdaaa6514040e60/tools/gn/bootstrap/bootstrap.py

The following revision refers to this bug:
  https://chromium.googlesource.com/infra/infra/+/655dc0d069829c955b2d33d89aa6305ea1a8c3a2

commit 655dc0d069829c955b2d33d89aa6305ea1a8c3a2
Author: Raphael Kubo da Costa <raphael.kubo.da.costa@intel.com>
Date: Tue Nov 13 16:09:29 2018

publish_tarball: Stop passing --no-sysroot to gn's gen.py

https://gn-review.googlesource.com/c/gn/+/3200 removed this option from GN
and moved to not downloading the sysroot from gen.py at all, so all our
builds were failed since we always clone GN at its latest commit.

Bug:  904350 
Change-Id: Ied8f0ec5b24a0aafe337cb14e1bdc5442c02576a
Reviewed-on: https://chromium-review.googlesource.com/c/1333687
Reviewed-by: Michael Moss <mmoss@chromium.org>
Commit-Queue: Raphael Kubo da Costa <raphael.kubo.da.costa@intel.com>
Cr-Commit-Position: refs/heads/master@{#18959}
[modify] https://crrev.com/655dc0d069829c955b2d33d89aa6305ea1a8c3a2/recipes/recipes/publish_tarball.expected/basic.legacy.json
[modify] https://crrev.com/655dc0d069829c955b2d33d89aa6305ea1a8c3a2/recipes/recipes/publish_tarball.expected/clang-no-fuchsia.json
[modify] https://crrev.com/655dc0d069829c955b2d33d89aa6305ea1a8c3a2/recipes/recipes/publish_tarball.py
[modify] https://crrev.com/655dc0d069829c955b2d33d89aa6305ea1a8c3a2/recipes/recipes/publish_tarball.expected/basic.json

The pending builds are now proceeding as expected now. See, for example, https://ci.chromium.org/buildbot/chromium.infra.cron/publish_tarball/14017

Fixing the bot was easier than I thought because it doesn't actually use Chromium's bootstrap.py; instead, it calls GN's gen.py directly.

Packagers who build their own GN will need to actually _start_ passing --with-sysroot to bootstrap.py for all releases prior to 72.0.3610.0, which is the first to contain the commit from comment #2 (until then, by default bootstrap.py passes --no-sysroot to gen.py unless --with-sysroot is passed to bootstrap.py itself).