### Description

Currently, the `airflow variables export` command requires an explicit file path and does not support output to stdout. However connections can be printed to stdout using `airflow connections export -`. This inconsistency between the two export commands can lead to confusion and limits the flexibility of the variables export command.

### Use case/motivation

To bring some consistency, similar to connections, variables should also be printed to STDOUT, using `-` instead of filename. 

### Related issues

_No response_

### Are you willing to submit a PR?

- [X] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

action="store_true",
)
ARG_CONTINUE_ON_FAILURES = Arg(
    ("--continue-on-failures",),
    help=("if set, the backfill will keep going even if some of the tasks failed"),
    action="store_true",
)
ARG_DISABLE_RETRY = Arg(
    ("--disable-retry",),
    help=("if set, the backfill will set tasks as failed without retrying."),
    action="store_true",
)
ARG_RUN_BACKWARDS = Arg(
    (
        "-B",
        "--run-backwards",
    ),
    help=(
        "if set, the backfill will run tasks from the most "
        "recent day first.  if there are tasks that depend_on_past "
        "this option will throw an exception"
    ),
    action="store_true",
)
ARG_TREAT_DAG_AS_REGEX = Arg(
    ("--treat-dag-as-regex",),
    help=("if set, dag_id will be treated as regex instead of an exact string"),
    action="store_true",
)
ARG_SHOW_DAGRUN = Arg(