upgrade webpack4 to webpack5 with error

[wlgmy]

Describe the bug
step1:npx sb@next upgrade --prerelease
step2: npm i -D @storybook/builder-webpack5@next
step3: add config in ./storybook/main.js
module.exports = {
core: {
builder: "webpack5",
},
};
step4: npm run storybook
then,I got this error:
Error: Compiling RuleSet failed: Unexpected property test in condition (at ruleSet[1].rules[1].resource.test: resource => {
currentResource = resource
return true
})

To Reproduce
Link to a reproduction repo that demonstrates the bug, plus instructions on how to trigger it.

System
Please paste the results of npx sb@next info here.
Environment Info:

System:
OS: macOS 10.15.7
CPU: (8) x64 Intel(R) Core(TM) i7-8557U CPU @ 1.70GHz
Binaries:
Node: 14.15.3 - ~/.nvm/versions/node/v14.15.3/bin/node
Yarn: 1.22.10 - /usr/local/bin/yarn
npm: 6.14.9 - ~/.nvm/versions/node/v14.15.3/bin/npm
Browsers:
Chrome: 90.0.4430.93
Safari: 13.1.3
npmPackages:
@storybook/addon-actions: ^6.3.0-alpha.17 => 6.3.0-alpha.17
@storybook/addon-essentials: ^6.3.0-alpha.17 => 6.3.0-alpha.17
@storybook/addon-links: ^6.3.0-alpha.17 => 6.3.0-alpha.17
@storybook/addon-viewport: ^6.3.0-alpha.17 => 6.3.0-alpha.17
@storybook/builder-webpack5: ^6.3.0-alpha.17 => 6.3.0-alpha.17
@storybook/vue: ^6.3.0-alpha.17 => 6.3.0-alpha.17
npmGlobalPackages:
@storybook/cli: 6.1.11
Additional context
Add any other context about the problem here.

[shilman]

Do you have a repro repo you can share?

[wlgmy]

https://github.com/wlgmy/storybook_webpack5.git
I write a demo to repro this case.

[shilman]

@wlgmy updated migration instructions here #15482 and tested successfully in your repro

[wlgmy]

I close this issue by: npm install webpack@5 --save-dev