swift

6c3dc31b - [build-script] Make sure that we build using an external compiler-rt on /all/ platforms, not just OS X.

[build-script] Make sure that we build using an external compiler-rt on /all/ platforms, not just OS X. This is important for a few reasons: 1. It ensures that on all platforms we use the just built clang to compile compiler-rt. This ensures that the clang used to compiler-rt has all of the features necessary to compile compiler-rt in the face of changes in the underlying implementation. 2. It ensures that all platforms build compiler-rt in the same manner.