Reland "Roll GN from 55ad154c..dfcbc6fe"

This is a reland of 32b629e77d005e642367b11e1f31edc5a1d73110

Original change's description:
> Roll GN from 55ad154c..dfcbc6fe
>
> Generated by //tools/gn/roll_gn.py
>
> https://gn.googlesource.com/gn/+log/55ad154c..dfcbc6fe
>
>     dfcbc6fe [xcode] Fix detection of XCTests by Xcode 12.0+
>     55e535a6 Remove `set_sources_assignment_filter` function
>     8fe02009 Add "else" to the list of gn keyword
>     d7cf6238 Address readme feedback.
>     ef13fe92 Change python to python3
>     09c9e5ee Fix some typos
>     335dd456 Fix build for riscv64 arch
>     94bda7cc Reword command format error messages
>     5f30bbf9 Add more README documentation.
>
> Bug: 1018739, 1174473, 1071055, 1103230
> Change-Id: I7af4db983f6a3ade9e667bf4ec9a55387655b7f1
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2681945
> Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
> Commit-Queue: Dirk Pranke <dpranke@google.com>
> Reviewed-by: Dirk Pranke <dpranke@google.com>
> Cr-Commit-Position: refs/heads/master@{#852251}

Bug: 1018739
Bug: 1174473
Bug: 1071055
Bug: 1103230
Change-Id: I388c0e284703941853c8951a762bb03d71cf4d0f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2684902
Commit-Queue: Dirk Pranke <dpranke@google.com>
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Cr-Commit-Position: refs/heads/master@{#853621}
GitOrigin-RevId: cd9bb069a0747d25a0b9758660761d5aa476d54e
1 file changed