We were making the initial `generateBuildGraph` call in `SourceKitLSPServer` from a `Task`. This means that `generateBuildGraph` could be executed after `waitForUpToDateBuildGraph` was called by `SemanticIndexManager`. Thus `waitForUpToDateBuildGraph` returned immediately and no files were background indexed.
Make `generateBuildGraph` immediately schedule a package reload for SwiftPM build systems instead of doing the hop through a `Task`, fixing the race condition.
rdar://135551812
4d1fa7a7ee