Checking out chromium release branch from scratch on Ubuntu 20.04

checkout.sh

#!/bin/bash

# Ref:
# https://chromium.googlesource.com/chromium/src/+/master/docs/#checking-out-and-building
#
# Note: the instructions say to use "fetch --nohooks chromium" but we'll do it
# manual here since we want to fetch the minimal amount of data and fetch a
# release branch instead of the tip of tree.

set -eux

# Where to checkout:
BASEDIR=$HOME/checkout_root
# Release to build:
REVISION=89.0.4364.1
# Set it to skip sync and install.
SKIP_SYNC_AND_INSTALL=1

# If this fails, sudo apt install python2:
python2 -c pass
# If this fails, sudo apt install python:
python -c pass
# Make sure you have git installed.
git help > /dev/null


cd $HOME
mkdir -p $BASEDIR
if [ ! -d $BASEDIR/depot_tools ]; then
  cd $BASEDIR
  git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git
fi
PATH=$BASEDIR/depot_tools:$PATH


mkdir -p $BASEDIR/chromium
cd $BASEDIR/chromium
if [ ! -d $BASEDIR/chromium/src ]; then
  # If starting from scratch, do not skip anything.
  SKIP_SYNC_AND_INSTALL=

  # For faster performance, use an authenticated URL:
  #   https://chromium.googlesource.com/a/chromium/src
  # It is determined with the /a/ prefix. To get the git cookies to
  # authenticate, visit this URL in a web browser, and it will provide a command
  # you can run to set it up in git. It's required if you want to contribute a
  # change.
  #
  # The following is using unauthenticated flow, which has less quota and will
  # be much slower.
  gclient config https://chromium.googlesource.com/chromium/src

  # A github clone:
  #gclient config --unmanaged https://github.com/maruel/chromium --name src
fi

if [ "$SKIP_SYNC_AND_INSTALL" = "" ]; then
  # Do a minimal checkout with no history. This will significantly reduce the
  # checkout size.
  # In practice with a combination of very fast internet and even with a very fast
  # 35Gbps SSD, writing files to disk will take more time than downloading the
  # repos... This fetches 126 git repositories. $BASEDIR/chromiumTook over 70 minutes here.
  time gclient sync --no-history --revision $REVISION
fi

# This should output over 45G.
du -h -s $BASEDIR/chromium

cd $BASEDIR/chromium/src

if [ "$SKIP_SYNC_AND_INSTALL" = "" ]; then
  # Install build dependencies. Skip when re-running so you don't have to sudo
  # every time.
  # Warning: installs a bunch of packages.
  ./build/install-build-deps.sh
fi

gn gen out/default

# Optimize our build:
cat > out/default/args.gn << EOF
# Do not build Native Client.
enable_nacl=false
# Build in Release but without LTO (very slow).
is_debug=false
# I don't plan to debug, so skip debug symbols.
symbol_level=0
EOF

# Expect something around 1680 minutes of user time and 65 minutes of kernel
# time. Divide by the number of logical cores.
time autoninja -C out/default chrome