fix: the --base option not work

[byyuurin]

Description

I noticed that vite-ssg build provides the --base option, but I found that it doesn't work as expected when I tried to use it.

Here are the tests I conducted after fixing this issue:

• Set base in vite.config.ts and perform a build to confirm the result.
• Set ssgOptions.base in vite.config.ts and perform a build to confirm the result.
• Add --base to vite-ssg build command and perform a build to confirm the result.
• Add --mode to vite-ssg build command and perform a build to confirm the result.
• Add both --mode and --base to vite-ssg build command and perform a build to confirm the result.
• Add NODE_ENV and --mode to vite-ssg build command and perform a build to confirm the result.

Linked Issues

339 #340 #341

[antfu]

Can you help resolve the conflicts? Thanks

[byyuurin]

Ok, updated.

[foxxyz]

Nice work, @byyuurin! thank you @antfu 🙏🏽