Paths in Git Bash on Windows don't work

### Reproduction

`windows-test.mjs`:

```javascript
import { $ } from 'zx'
import path from 'node:path'
import { fileURLToPath } from 'url'

const __dirname = path.dirname(fileURLToPath(import.meta.url))

$.verbose = true
await $`zx --version`
await $`mkdir -p ${path.join(__dirname, 'AA-zx-test')}`
await $`mkdir -p BB-zx-test`
await $`ls -l | grep zx-test`
```

### Actual behavior

```
await $`mkdir -p ${path.join(__dirname, 'AA-zx-test')}`
```

silently does nothing on Windows in Git Bash.

The generated command

```
mkdir -p $'C:\\git\\frontend_main\\apps\\acheron\\AA-zx-test'
```

appears to be correct though, as running it manually works.


Works without issue on macOS & Linux in Bash.

### Expected

```
await $`mkdir -p ${path.join(__dirname, 'AA-zx-test')}`
```

working, as on other OS.