The basic infrastructure to support this is now in place. Add a new
board that uses the experimental coreos/amd64/usr profile /usr based
disk layouts. This is just enough to successfully build images, they
aren't bootable yet.
When calling update_chroot with --usepkg --nogetbinpkg the default
emerge command line will force binary packages for the toolchain but if
the packages are not available locally building via crossdev is
required. Since the crossdev bootstrap process rebuilds the toolchain a
couple times with different use flags if binary packages are forced the
second stages gets skipped resulting in a broken gcc and glibc install.
Although it didn't seem to be causing any bugs the global variables in
toolchain_util conflicted with some names used elsewhere. Clean that up
by adding an S to the array names that didn't already have one.
When calling update_chroot with --nousepkg it is silly to always force a
rebuild of the cross toolchain. Change the test to work regardless of
whether binary packages are enabled by checking if anything needs to be
built from source.
Now this code can be shared with setup_board. Only required if
setup_board is called with --nousepkg which is rare to never but feels
like the correct thing to do. Alternatively setup_board could always
use binary packages (as it basically does now).
This replaces the cross-toolchain compile step in bootstrap_sdk and adds the
ability to build native toolchains using the cross toolchain. This is just
the first step towards actually providing the native toolchain in a container.
