Revert "Roll GN from 81ee1967 to 8c7f4910"

This reverts commit 221c6f3dad0073f21079673f7b05a5ac88e13a95.

Reason for revert: ChromeOS build failures; see https://crbug.com/974835.

Original change's description:
> Roll GN from 81ee1967 to 8c7f4910
> 
> https://gn.googlesource.com/gn.git/+log/81ee1967..8c7f4910
> 
> 8c7f491 rust: fix build on older clang by Tomasz Śniatowski
> 8f8178c Escape prerequisites filenames in build.ninja.d depfile by samogot
> 89d5ef5 Minor fixes to tracing by Julie Hockett
> ae93998 An example Rust build by Julie Hockett
> 80a5dc0 Ninja rules for Rust by Julie Hockett
> e906492 Rust GN target generation by Julie Hockett
> 586b028 Rust compilation tool and toolchain support by Julie Hockett
> ed8b690 rust_library and Rust-specific variables by Julie Hockett
> 5b16fb9 Rust substitutions and config values by Julie Hockett
> b89110a Move SourceFileTypeSet to Target by Julie Hockett
> 95a92a9 [espace.h] fix comment by Takuto Ikuta
> 17cc456 json_project_writer: Output response_file_contents for action and action_for_each by Kimmo Kinnunen
> 36c66bf Add additional surce files and example the list of acceptable files by Julie Hockett
> 04f5df5 [args] Fix gn args unstable output by Haowei Wu
> bc3fe2a [gen.py] Use relative -I switches and source paths by Roland McGrath
> 8730b0f Disallow non-buildable sources in binary targets by Tom Anderson
> 0d038c2 Cache source file type in SourceFile by Tom Anderson
> 
> BUG=964411
> R=​dpranke
> 
> Change-Id: Ib9ea522a075fba2ca81b91ab347731a7829901b9
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1650093
> Reviewed-by: Nico Weber <thakis@chromium.org>
> Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
> Auto-Submit: Thomas Anderson <thomasanderson@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#669546}

TBR=thakis@chromium.org,dpranke@chromium.org,thomasanderson@chromium.org

Change-Id: Icf28406f4f204a5814cbd0d305f2508240df0dc5
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 964411
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1660809
Reviewed-by: Sidney San Martín <sdy@chromium.org>
Commit-Queue: Sidney San Martín <sdy@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#669716}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 47efe3b5cbbf30b48870cda297b585d5d17f1820
1 file changed