Log Message:
amazon-ecs-cli: fix builds with recent Go versions

This package (which hasn't had a subsequent release from upstream) will
no longer build when being treated as a "module" by recent Go versions
(and related pkgsrc definitions). It seems non-trivial to address this
(simply trying to add go.mod and such then leads to other errors, e.g.,
recent Go objecting to API versioning practices in code bundled by
upstream), so to get this building again for now, use the old "package"
approach instead.