Allows end-users to export final build content or rootfs to external formats.
By default, a local container image is created from the build result. The --output (or -o) flag allows you to override this behavior, and a specify a custom exporter. For example, custom exporters allow you to export the build artifacts as files on the local filesystem instead of a Container image, which can be useful for generating local binaries, code generation etc.
The value for --output is a CSV-formatted string defining the exporter type and options. Currently, local and tar exporters are supported. The local exporter writes the resulting build files to a directory on the client side. The tar exporter is similar but writes the files as a single tarball (.tar).
```console
buildah build --output type=local,dest=dir .
buildah build --output type=tar,dest=rootfs.tar .
buildah build -o dir .
```
Reference: https://docs.docker.com/engine/reference/commandline/build/#custom-build-outputs
Signed-off-by: Aditya R <arajan@redhat.com>
d0336f2147