Due to the assumption of building from a git repository inherent in the
Makefile targets, update the documentation to limit source code archive
builds to the `go build` commands.
Note that it may be possible to update hack/build.sh to cope with
building outside a git repository, but there are a number of questions
to answer regarding how to populate the buildinfo info, and that is a
larger discussion than ensuring we can build the binary from the sources
in the source code archive.
Signed-off-by: Darren Hart <dvhart@vmware.com>
9df3947745