swift234

[SR-1788] Add -driver-time-compilation option (#4367)

Add an option to print the time it takes each driver task to complete.

Here's an example of the output:

```
$ swiftc -driver-time-compilation \
         -emit-library -module-name Crispix \
         Crispix/A.swift Crispix/B.swift Crispix/C.swift
===-------------------------------------------------------------------------===
                           Driver Time Compilation
===-------------------------------------------------------------------------===
  Total Execution Time: 0.0000 seconds (0.0875 wall clock)

   ---Wall Time---  --- Name ---
   0.0245 ( 28.0%)  link /path/to/Crispix/A.swift /path/to/Crispix/B.swift /path/to/Crispix/C.swift
   0.0211 ( 24.1%)  compile /path/to/Crispix/A.swift
   0.0209 ( 23.9%)  compile /path/to/Crispix/B.swift
   0.0176 ( 20.1%)  compile /path/to/Crispix/C.swift
   0.0035 (  4.0%)  swift-autolink-extract /path/to/Crispix/A.swift /path/to/Crispix/B.swift /path/to/Crispix/C.swift
   0.0875 (100.0%)  Total
```