ci: fixes to actions caches

[davidhewitt]

This attempts to fix some issues I'm seeing in our CI caches:

• The cross-compilation jobs are unintentionally sharing cache for different build targets. I think this has caused the issue we are currently seeing with GLIBC linking in the x86_64 linux job.
• The cache cleanup job is not being granted write permissions to delete caches. If I'm reading the GitHub Actions docs correctly the pull_request_target runs using the base branch (i.e. main), so can be trusted to grant write permissions.
• The cargo-semver-checks cache key starts with a dash, like -semver-<whatever> and the gh actions-cache delete command was treating it as a flag, which it did not recognize. Hopefully by passing the key after -- will force it to treat it positionally.

cc @obi1kenobi - you might be interested to know that the leading dash in the cargo-semver-checks cache key can be a footgun for automated tooling.

Will proceed straight to merge as I think there's nothing contentious here and it should unblock CI.

[obi1kenobi]

cc @obi1kenobi - you might be interested to know that the leading dash in the cargo-semver-checks cache key can be a footgun for automated tooling.

Ah interesting, thanks for the ping! I'll look into this.

[obi1kenobi]

Published an updated action (v2.4) that won't use a leading dash. As is usual practice, I re-pointed the v2 tag to v2.4 so it'll get picked up automatically for most users.

Thanks for letting me know!

[davidhewitt]

Great, thanks! 👍