Make assets:install smarter with symlinks

| Q             | A
| ------------- | ---
| Bug fix?   | no
| New feature?      | yes
| BC breaks?      | no
| Deprecations?      | no
| Tests pass?      | -
| Fixed tickets     | #11297
| License     | MIT
| Doc PR | -
We need someone on a VM that has a Windows host machine (and where the project files are shared with the host machine) to try this and see if this properly catches the failure: https://github.com/symfony/symfony/issues/11297#issuecomment-48075759