Provide compiler error when not in verbose

[orta]

To get any useful information (which you need to continue) with a project, I have to re-run with --verbose

 ~/d/p/o/s/a/Marathon $  marathon run danger/danger-swift 
💥  Failed to compile script

Running with --verbose:

 !  ~/d/p/o/s/a/Marathon $  marathon run danger/danger-swift --verbose
🏃  Cloning https://github.com/danger/danger-swift.git...
   $ cd "/Users/orta/.marathon/Scripts/Temp/https:--github.com-danger-danger-swift.git/" && git clone https://github.com/danger/danger-swift.git clone -q

   $ cd "/Users/orta/.marathon/Scripts/Temp/https:--github.com-danger-danger-swift.git/clone/" && /usr/bin/env xcrun --sdk macosx swift build -C /Users/orta/.marathon/Scripts/Temp/https:--github.com-danger-danger-swift.git/clone/ --enable-prefetching
   swift-build: error: Package requires minimum Swift tools version 4.0.0. Current Swift tools version is 3.1.0
💥  Failed to compile script

Ideally the swift-build: error: Package requires minimum Swift tools version 4.0.0. Current Swift tools version is 3.1.0 would show without running verbose

[JohnSundell]

Totally agree 👍 just like how we bubble up standard build errors (even in non-verbose mode) we should do the same for SPM errors. Especially for tools version, since that's a quite common error to encounter.