Fix loading package manifest

[ctreffs]

This PR fixes a crash when running swift-bundler bundle or run with added -d or --directory argument pointing to a package-path other than the current directory.

swift-bundler bundle --directory <path_to_package_root> <target_name> produces error:

info: Loading package manifest
error: Failed to run '/usr/bin/env swift package describe --type json': The process returned a non-zero exit status (1)
error: Could not find Package.swift in this directory or any of its parent directories.


info: Use -v to get more error details
Program ended with exit code: 1

Solution is to include the already provided packageDirectory argument in loadPackageManifest (SwiftPackageManager.swift:438) to the swift package command invocation.

[stackotter]

Thanks for this fix 🙏