keystone: windows compatibility: monorepo does not symlink

From @1337cookie https://github.com/keystonejs/keystone-5/pull/1463#issuecomment-519957463

@MadeByMike and I saw the same issue. It is not seen when using admin privillages but that is definitely not advised and not a solution.

C:\Users\user\Documents\web\keystone-5>bolt
⚡️   bolt v0.23.6 (node v10.16.1)
�   [1/4] Validating project...
�   [2/4] Installing project dependencies...
$ C:\Users\user\AppData\Local\Yarn\Data\global\node_modules\bolt\node_modules\.bin\yarn config get user-agent yarn/1.17.3 npm/? node/v10.16.1 win32 x64
yarn install v1.17.3
[1/4] Resolving packages...
[2/4] Fetching packages...
info fsevents@1.2.7: The platform "win32" is incompatible with this module.
info "fsevents@1.2.7" is an optional dependency and failed compatibility check. Excluding it from installation.
info fsevents@1.2.4: The platform "win32" is incompatible with this module.
info "fsevents@1.2.4" is an optional dependency and failed compatibility check. Excluding it from installation.
[3/4] Linking dependencies...
warning "apollo-server-express > apollo-server-core > apollo-tracing@0.5.2" has incorrect peer dependency "graphql@0.10.x - 14.1.x".
warning "graphql-playground-react > react-codemirror@1.0.0" has incorrect peer dependency "react@>=15.5 <16".
warning "graphql-playground-react > react-codemirror@1.0.0" has incorrect peer dependency "react-dom@>=15.5 <16".
[4/4] Building fresh packages...
$ yarn build:build-field-types && preconstruct dev && node ./packages/build-field-types/bin.js dev  && yarn run --silent contributing-guide
yarn run v1.17.3
$ rimraf packages/build-field-types/lib && babel packages/build-field-types/src --out-dir packages/build-field-types/dist --ignore '**/__tests__/**/*','**/__mocks__/**/*'
Successfully compiled 42 files with Babel.
Done in 4.41s.
� info project is valid!
� error { [Error: EPERM: operation not permitted, symlink 'C:\Users\user\Documents\web\keystone-5\packages\arch\packages\alert\src\index.js' -> 'C:\Users\user\Documents\web\keystone-5\packages\arch\packages\alert\dist\alert.cjs.js.flow']
� error   errno: -4048,
� error   code: 'EPERM',
� error   syscall: 'symlink',
� error   path:
� error    'C:\\Users\\user\\Documents\\web\\keystone-5\\packages\\arch\\packages\\alert\\src\\index.js',
� error   dest:
� error    'C:\\Users\\user\\Documents\\web\\keystone-5\\packages\\arch\\packages\\alert\\dist\\alert.cjs.js.flow' }
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/install for documentation about this command.
error Error: spawn C:/Users/user/AppData/Local/Yarn/Data/global/node_modules/bolt/node_modules/.bin/yarn ENOENT
error     at notFoundError (C:/Users/user/AppData/Local/Yarn/Data/global/node_modules/cross-spawn/lib/enoent.js:11:11)
error     at verifyENOENT (C:/Users/user/AppData/Local/Yarn/Data/global/node_modules/cross-spawn/lib/enoent.js:46:16)
error     at ChildProcess.cp.emit (C:/Users/user/AppData/Local/Yarn/Data/global/node_modules/cross-spawn/lib/enoent.js:33:19)