Gracefully handle inconsistent

Why is this needed?

If a Swift Package contains a single target, for example Foo, SwiftPM can read the sources fro Sources/ sub-directories that don’t have that name, for example Bar. Unfortunately, this is a behavior that our integration logic doesn’t account for, causing the integration of some packages via .external to fail. We should make sure we can handle that scenario in the same way SwiftPM does.

Steps to address the need

• Create a Tuist project
• Create a local package with a single target whose sources folders doesn’t match the package name
• Depend on the package target via .external.
• Run tuist install.
• It’ll fail when it should not.