We introduce a WithSpecFromFile option combinator to allow creation
simpler creation of OCI specs from a file name. Often used as the first
option in a `SpecOpts` slice, it simplifies choosing between a local
file and the built-in default.
The code in `ctr run` has been updated to use the new option, with out
changing the order of operations or functionality present there.
Signed-off-by: Stephen Day <stephen.day@getcruise.com>
This allows Go to build third party packages correctly without vendoring
issues what want to create their own SpecOpts.
Fixes#2289
Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
