dib_[environment|args] manifest files are currently generated by the
base element and then moved by the manifest element.
This creates too many corner cases -- if you don't include the base
element (we are trying to empty it ATM) you don't get the env/args
saved at all; if you include base but don't include the manifest
element they're saved to /etc, but if you do have the manifest element
they're moved to the manifest dir.
Move generation of these into the manifest element directly and update
the documentation to reflect this. In practice this doesn't change
things, because the "manifests" element gets pulled in via deps for
most builds.
Change-Id: I3f23037058137d166b29f0b70fd1a02c22c07fc8
Signed-off-by: Andreas Florath <andreas@florath.net>
