Use -X ldflags to set dockerversion package vars
Use -X ldflags to set dockerversion package vars

This eliminates the need to lay down an auto-generated file.
IIRC this was originally hadded for gccgo which we no longer support.

Signed-off-by: Brian Goff <dc73d0991b982a8303e713ef531a313af77e242a@gmail.com>

moby/term