swift

91473cc7 - [5.7] IRGen: Add a frontend option to force single LLVM module emission in multithreaded mode

[5.7] IRGen: Add a frontend option to force single LLVM module emission in multithreaded mode This allows to experiment with single module LLVM emission without having to change drivers that expect multiple output files. rdar://94744623 (cherry picked from commit 821ba4707979019247b4c7114072ac1eba705b85)