Enable buildah debug logs

Description

Other jobs make use of the TRACE environment variable to enable lower level debug logging. For example, skopeo and kaniko in this component both get debug logging enabled if TRACE is set.

The use of buildah does not currently use the TRACE variable, and this would be helpful to debug issues when building with buildah.

Implementation ideas

buildah has a command line flag to adjust the logging:

--log-level string                     the log level to be used, one of "trace", "debug", "info", "warn", "error", "fatal", or "panic" (default "warn")

It may make sense to implement this similar to how was done for e.g. kaniko:

/kaniko/executor ${TRACE+--verbosity debug} ...

For buildah would become:

buildah ${TRACE+--log-level debug} build ...