## What?

In the past folks on the team have reported that anytime the SWC /
Turbopack binary changes they had to suddenly run `pnpm build-native` in
`packages/next-swc`, even though they didn't build from source before.
While investigating optimizing packing for tests I found that it's
copying the native binary into the original repository not the temporary
repository, which then keeps the file there, even after the tests
finish. This fixes the path to use the tmp repository instead.


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Closes NEXT-3157

Before: 25.71s

![CleanShot 2024-04-23 at 12 19
42@2x](https://github.com/vercel/next.js/assets/6324199/3a0ebb81-ac55-4b0c-8bfc-9a61ce138e6f)

After: 11.05s (-57%)

![CleanShot 2024-04-23 at 12 16
35@2x](https://github.com/vercel/next.js/assets/6324199/d7b6cd4c-d1e4-4dc2-a423-20b539186d25)

Currently the system for isolation looks like this:

- Copy `packages` folder to an isolated directory
- Run `pnpm pack` for all folders in `packages`
- Collect the pack files, add them as `dependencies` in package.json of
the isolated application
- Run `pnpm install`

Because the `next-swc` (Turbopack + SWC, yes we still need to rename the
package) binary file is quite large in development (900MB+) it means we
have to copy, then zip (pnpm pack), then unzip (pnpm install) that
binary, which takes about 3+ seconds in each step.

The change in this PR is to skip the copy/zip/unzip completely by
providing the folder path for the binary directly to Next.js, as it's a
binary we don't need the special isolation for this, it's already
standalone so running it directly allows us to skip 14,6 seconds of work
that is required for each isolated test in development.

This will likely have little effect on CI times as we already do some
tricks like only running the packing at the start of the CI process.
Only thing that could be better and is probably worth doing is adopting
this change for the time it saves for unzipping, that's almost 4 seconds
per test still.

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Closes NEXT-3200

---------

Co-authored-by: JJ Kasper <jj@jjsweb.site>

Noticed while testing turbopack version of tests that we weren't loading
the correct swc binary since this path wasn't absolute and was just the
relative path in `node_modules`.

---------

Co-authored-by: Zack Tanner <1939140+ztanner@users.noreply.github.com>

### What

this was the way we run ci on turbopack's repo and to get the latest
test results, which isn't required anymore.