This will likely be the default in Xcode 10, so we should at least make sure there aren't any issues with the existing projects and template.
The new build system was on average 28% faster with clean builds and 82% faster on incremental builds. “Live issues” during editing are a major pain point for Swift. The tools crash, issue presentation is slow and often just plain wrong. While there is no way to measure the performance of live issues, it was clearly faster and more stable during editing than the default build system.
This will likely be the default in Xcode 10, so we should at least make sure there aren't any issues with the existing projects and template.
https://github.com/fastred/Optimizing-Swift-Build-Times#use-the-new-xcode-build-system