consider for real if the calls to the compiler, linker should be factored out into a toolchain

[gizmomogwai]

the toolchain knows best, what to do for a specific compiler.
if all compiler support @-arguments for long commandline the toolchain is a good place
to put some more logic on when to use @ and when to use direct spawn, also regarding ruby versions and os!
has_sources, has_dependencies, executable and source_library already have a lot to care about. so this is a good thing to put
into another class!
to be discussed