Doom purge doesn't purge straight build directory on version switch

### What did you expect to happen?

If I have
`.local/straight/build-28.0.50` and `.local/straight/build-28.0.60` folders

And I run
`doom sync -p`

Then, as I'm using `28.0.60` version of emacs, `build-28.0.50` is deleted

### What actually happened?

The `build-28.0.50` directory is not deleted, and I suspect this messes up with load-path and load-order (since I had a lot of `xxxx.el is newer than byte-compiled file` warnings)

### Describe your attempts to resolve the issue

Deleting the old `build-28.0.50` file manually seems to solve the issue (i.e. I have new bugs to deal with, solely on me :( )

### Steps to reproduce

1. Keep 2 versions of Emacs
2. `EMACS=emacs-28 doom sync`
3. `EMACS=emacs-29 doom sync -up`

### System Information

http://0x0.st/-7ht.txt