In the original implementation (https://github.com/apple/swift/pull/36377), using `--infer` accidentally disables the `earlyswiftdriver` product (`before_impl_product_classes` set to always empty). This change fixes that and makes sure early SwiftDriver is always built, regardless of whether or not `--infer` is used.
This change also ensures that `install_all` setting triggered by `--infer` does not affect products which specify `is_ignore_install_all_product` to return True. This is useful for products which should not be installed into the toolchain (corresponding build products that use the just-built toolchain are the products that get installed, e.g. `swiftdriver` to `earlyswiftdriver`).