Make Logos stderr output similar to clang

[kirb]

Having Logos errors follow the same format as clang will make them a bit easier to spot amongst the sea of other colors in the build output, and will also match Xcode’s regexes for error output to ensure it comes up nicely in the warnings tab for people using Theos/Logos via Xcode. (ibtool and some other tools invoked by a typical app build process do the same.)