Fix background indexing behavior if a source file is included in two targets via a symlink

Consider the following scenario: A project has target A containing A.swift an target B containing B.swift. B.swift is a symlink to A.swift. When A.swift is modified, both the dependencies of A and B need to be marked as having an out-of-date preparation status, not just A.

Sources/BuildSystemIntegration/SwiftPMBuildSystem.swift

@@ -587,7 +587,7 @@ package actor SwiftPMBuildSystem: BuiltInBuildSystem {
         SourceItem(
           uri: DocumentURI($0),
           kind: $0.isDirectory ? .directory : .file,
-          generated: false,
+          generated: false
         )
       }
       result.append(SourcesItem(target: target, sources: sources))