passthrough-arguments leads to trailing slashes in argument key on Windows

Description: Using -P, --passthrough-arguments leads to trailing slashes in argument key on Windows (and stackblitz.com).

On local Mac doesn't reproduce. If adding only the key without value (e.g. yarn test --key) doesn't reproduce as well.

Expected Behavior: Argument key should not have a trailing slash when specifying argument value.

Environment: concurrently v7.6.0 OS: Windows 10 Node v16.14.2

Reproduction: stackblitz in terminal type: npm run test -- --key=value or yarn test --key=value

See Images attached: