CRA 2.0: urls in static files not correct when homepage="."

Created by: bradfordlemley

Is this a bug report?

Yes

Steps to Reproduce

1. Use react-scripts@2.0.0-next.3e165448
2. In app's package.json, set "homepage": "."
3. In App.css, add a url to a static file, e.g., background-image: url(./logo.svg)
4. yarn build

Expected Behavior

build/static/css/main.[hash].chunk.css should have: background-image:url(../../static/media/logo.5d5d9eef.svg)

Actual Behavior

build/static/css/main.[hash].chunk.css has: background-image:url(static/media/logo.5d5d9eef.svg)