Update sass to work around CRA build crashes

[BPScott]

WHY are these changes introduced?

Fixes #2629

The current version of CRA' s build uses a version of https://github.com/postcss/postcss-custom-properties that crashes when it comes across var()s inside calc()s a very specific order of calls: top:calc(var(--control-border-width)*-1). See #2629 (comment) for more info. This has been fixed in the newest version of postcss-custom-properties but that's not made its way into CRA (via postcss-preset-env) and probably won't be for some time.

WHAT is this pull request doing?

Flip the order of values (yes I know this sounds silly)

How to 🎩

Ask @dleroux nicely to see that there are no visual regressions.

• Do a build yarn run build
• Create a new CRA project with yarn create react-app testing
• Copy the build styles.css into the CRA app and import the styles from CRA's src/ index.js file and see if a build compiles using yarn run build

[github-actions]

💦 Potential splash zone of changes introduced to src/**/*.tsx in this pull request:

No significant changes to src/**/*.tsx were detected.

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[dleroux]

It looks like this is working Ben. The same approach is being used here: https://github.com/Shopify/polaris-react/blob/master/src/styles/foundation/_focus-ring.scss#L31 I assume this one will need to change as well?

[BPScott]

The same approach is being used here: https://github.com/Shopify/polaris-react/blob/master/src/styles/foundation/_focus-ring.scss#L31 I assume this one will need to change as well?

Funky. That's been in there for a while and hasn't caused crashes. Along with a bunch of other places, searching our codebase for calc(var(.

I've done some digging and it's not calc(var()) that's the problem and now I'm mad. #2629 (comment)

Changing calc(var(--control-border-width) * -1); to calc(-1 * var(--control-border-width)); should get this to compile.