pack-next: use default `--js-build` as option instead of `--no-js-build` (#77686)
Yargs automatically creates `--no-` variations of options. Using
`--no-js-build` as an option directly confuses it.
`--no-js-build` remains a valid cli argument.
Test Plan: Verify `pnpm pack-next` builds JS by default and `pnpm
pack-next --no-js-build` doesn’t.
Help now looks like this:
```
pack-next.ts
Options:
--help Show help [boolean]
--version Show version number [boolean]
--js-build Build JavaScript code (default). Use `--no-js-build` to skip
building JavaScript [boolean] [default: true]
-p, --project [string]
--tar Create tarballs instead of direct reflinks [boolean]
--compress How compress the binary, useful on platforms where tarballs
can exceed 2 GiB, which causes ERR_FS_FILE_TOO_LARGE with
pnpm. Defaults to "strip" on Linux, otherwise defaults to
"none". Requires `--tar` to be set.
[string] [choices: "none", "strip"]
```