Description
Original PEP518 spec (https://peps.python.org/pep-0518/#build-system-table) says:
The [build-system] table is used to store build-related data. Initially only one key of the table will be valid and is mandatory for the table: requires. This key must have a value of a list of strings representing PEP 508 dependencies required to execute the build system
while the packaging guide (https://packaging.python.org/en/latest/specifications/pyproject-toml/#declaring-build-system-dependencies-the-build-system-table)
The [build-system] table is used to store build-related data. Initially, only one key of the table is valid and is mandatory for the table: requires. This key must have a value of a list of strings representing dependencies required to execute the build system. The strings in this list follow the version specifier specification.