Bug Description

the license: field cannot be a license expression which does not allow to accurately depict the license of the main components of the rock.

my use case: #978

rust and cargo are dual licensed under MIT or Apache-2.0 and the rock also includes the gcc tolchain which is licensed under GPL-3.0

To Reproduce

license: (MIT OR Apache-2.0) AND GPL-3.0

Environment

n/a

rockcraft.yaml

n/a

Relevant log output

2025-09-25 18:48:56.052 Bad rockcraft.yaml content:
2025-09-25 18:48:56.053 - license (MIT OR Apache-2.0) AND GPL-3.0 not valid. It must be either 'proprietary' or in SPDX format. (in field 'license')