Apply lint config in exec configuration

[isaacparker0]

Previously lint_config was not applied for targets building in the exec configuration, but I think lint config should always be respected as it's the target's explicit intent. The original justification of preventing crates used in build scripts from generating warnings seems spurious to me, and it's not clear to me why target vs. exec configuration should affect how source code is linted. A real example where this is problematic:

• a codebase defines a lint config to disable a default rustc lint.
• now building some workspace crate in the exec configuration will always show that warning with no way to suppress it.