Some notes on ROOT: * The idea behind ROOT is that one can build a system with ROOT=/somewhere and then chroot into it or tar up /somewhere as a system image. It is not designed to allow the user to run /somewhere/usr/bin/foo. * ROOT can't be used correctly in src_*, since ROOT might be different when merging a binary package. For example, a binary package might be built with ROOT=/ and then installed onto a system using ROOT=/somewhere. * ROOT isn't used for library dependencies. When building, libraries, headers etc. on / have to be used. Cross-compiling etc is done by configuring the toolchain correctly, not by hacking ebuilds in a way that breaks binary packages. See also the discussion on bug #167285 for more info.
The 3rd part of this statement is incorrect. ROOT is exactly used for lib deps and includes.
