`npm run size` script fails on Windows

[stuartlong]

Is this a bug report or a feature request?

The git pre-push hook fails on Windows due to the npm run size script:

$ npm run size

> @cypress/[email protected] size E:\snapshot
> t="$(npm pack .)"; wc -c "${t}"; tar tvf "${t}"; rm "${t}";

't' is not recognized as an internal or external command,
operable program or batch file.
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! @cypress/[email protected] size: `t="$(npm pack .)"; wc -c "${t}"; tar tvf "${t}"; rm "${t}";`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the @cypress/[email protected] size script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     C:\Users\stuartlo\AppData\Roaming\npm-cache\_logs\2019-04-03T20_57_05_418Z-debug.log

• latest master
• Windows