Build is flaky

[nicksnyder]

Builds fail like this

yarn --frozen-lockfile
  | yarn workspace webapp run browserslist
  | yarn workspace sourcegraph run build
  | yarn workspace @sourcegraph/extensions-client-common run build
  | NODE_ENV=production yarn workspace webapp run build --color
  | GITHUB_TOKEN= yarn workspace webapp run bundlesize
  | yarn install v1.10.1
  | [1/5] Validating package.json...
  | [2/5] Resolving packages...
  | [3/5] Fetching packages...
  | info There appears to be trouble with your network connection. Retrying...
  | info There appears to be trouble with your network connection. Retrying...
  | info There appears to be trouble with your network connection. Retrying...
  | info There appears to be trouble with your network connection. Retrying...
  | info There appears to be trouble with your network connection. Retrying...
  | info There appears to be trouble with your network connection. Retrying...
  | info There appears to be trouble with your network connection. Retrying...
  | error An unexpected error occurred: "https://registry.npmjs.org/date-fns/-/date-fns-2.0.0-alpha.25.tgz: ESOCKETTIMEDOUT".
  | info If you think this is a bug, please open a bug report with the information provided in "/buildkite/builds/buildkite-agent-797f4d46cb-jcpn7-1/sourcegraph/.golang/sourcegraph/src/github.com/sourcegraph/sourcegraph/yarn-error.log".
  | info Visit https://yarnpkg.com/en/docs/cli/install for documentation about this command.
  | 🚨 Error: The command exited with status 1

https://buildkite.com/sourcegraph/sourcegraph/builds/23218#6ad76254-926d-40a3-8679-feffbb2af1c5

See also

• There appears to be trouble with your network connection. Retrying... yarnpkg/yarn#4890
• There appears to be trouble with your network connection. Retrying... yarnpkg/yarn#5259
• yarn install says There appears to be a trouble in your network connections. Retrying... yarnpkg/yarn#4333
• There appears to be trouble with your network connection. Retrying... yarnpkg/yarn#5848