Update the way we handle directories supplied by the user:
- the tarball directory is considered as a local copy, and tarballs are copied to a working area,
- the sources and build directories (CT_SRC_DIR and CT_BUILD_DIR) are now computed, and no longer an option,
- the build dir has been renamed from 'build' to 'targets'.
That should ease preparing a tarball of the resulting target.

 This is the README for crosstool-NG

 To get you started, hust enter:

   make help

 You can find a (terse and WIP) documentation in docs/.

 You can also point your browser to

   http://ymorin.is-a-geek.org/dokuwiki/doku.php?id=projects:crosstool