Print exceptions even when logging to a file

[tristanlabelle]

Currently failures look like the below and are hard to diagnose:

[cmake] -- changes to swiftwinrt.exe parameters detected
[cmake] -- running swiftwinrt.exe @SwiftWinRT.rsp
[cmake] CMake Error at SwiftWinRT.cmake:84 (execute_process):
[cmake]   execute_process failed command indexes:
[cmake] 
[cmake]     1: "Child return code: 1"
[cmake] 
[cmake] -- Configuring incomplete, errors occurred!

[z2oh]

Awesome!