As discussed in issue #8037, using `c_args` in `project()` leads to
`CFLAGS` not being respected, which is a common mistake. Document this
and suggest using `add_project_arguments()` instead.
Signed-off-by: John Levon <levon@movementarian.org>
The array of licenses is not clear, where and SPDX expression using AND
and OR is very clear, take for example this: `['Apache', 'GPLv2']`. What
does that mean? Any Apache license you like and GPLv2? Using a valid
SPDX license identifier however makes it extremely clear what is meant:
`'Apache-2.0 OR GPL-2.0-only'`. It is very clear that you mean, "this is
Apache 2.0, however, you can use as GPL-2.0 for the purpose of linking
it into your GPL-2.0 project".