swift

658c3a94 - [IRGen] Fix SynthesizedFileUnit.

[IRGen] Fix SynthesizedFileUnit. SynthesizedFileUnits are attached to a SourceFile. Make IRGen consistent with TBDGen: when processing a SourceFile, only process the attached SynthesizedFile. This avoids IRGen/TBDGen inconsistencies. Resolves TF-1249.