Currently, the `SORT` flag mandates the inclusion of at least the
`sort_by_first` argument in the grammar, despite the documentation[1]
indicating that `SORT` can be utilized without any arguments, defaulting
to sorting input sections by name. Fix this by modifying the grammar
to allow a default `SORT` and update a test accordingly.
[1] https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-guides/
linker-script-generation.html
Signed-off-by: Frantisek Hrbata <frantisek.hrbata@espressif.com>
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