npm run build doesn't create build directory, fails if it doesn't exist

[jscholes]

I recently needed to run npm run cleanup, to completely remove the build directory in order to avoid merge conflicts. This worked as expected, but when subsequently running npm run build, this was the result:

> [email protected] build L:\Dropbox\Dev\aria-at
> npm run create-all-tests && npm run review-tests


> [email protected] create-all-tests L:\Dropbox\Dev\aria-at
> cross-var node scripts/create-all-tests.js --testplan=$npm_config_testplan

The destination 'build' directory does not exist.
npm ERR! code ELIFECYCLE

If a command is provided to remove the build directory before rebuilding it, it seems suboptimal that rebuilding it then doesn't work without the additional step of manually recreating the directory. Particularly because Git doesn't allow you to commit an empty directory addition by default, so it's impossible to do something like:

npm run cleanup
git add --all .
git commit -m "Remove build directory"
git push

... and have the GitHub Actions workflow actually work.

CC @s3ththompson