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 | -
That's wrong. The symlink function always exists, even on Windows. What we need to check is whether we can use it safely or not.