fix(css): resolve at import from dependency basedir

[bluwy]

Description

Fix #12795

Whenever we resolve a @import, respect basedir passed.

Previously, basedir is always the root because we append the importer with a *:

vite/packages/vite/src/node/plugins/css.ts

Line 926 in a2b7a51

path.join(basedir, '*'),

But we check the importer existence when resolving a basedir:

vite/packages/vite/src/node/plugins/resolve.ts

Lines 696 to 706 in a2b7a51

	if (dedupe?.includes(pkgId)) {
	basedir = root
	} else if (
	importer &&
	path.isAbsolute(importer) &&
	fs.existsSync(cleanUrl(importer))
	) {
	basedir = path.dirname(importer)
	} else {
	basedir = root
	}

Because the * always make this not exists, basedir is always root.

This PR fixes this.

Additional context

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the PR Title Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

[stackblitz]

Run & review this pull request in StackBlitz Codeflow.