In case go build will see a need to call C++ (rather than C)
compiler, CXX env var need to be properly set (to osxcross wrapper).
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Remove referenced to developing on the host, we shouldn't support it.
Move script/validate to scripts/validate to be consistent.
Set the default target to be binary instead of clean.
Signed-off-by: Daniel Nephin <dnephin@docker.com>