False positive for C-like enums involving configuration-dependent constants

[DemiMarie]

My project includes C-like enums with discriminants that depend on the pointer width. This is done with cfg(target_pointer_width = "x") on consts. As a result, I get false positives from enum_clike_unportable_variant.

[oli-obk]

This probably requires rustc support to detect whether something was cfg'ed, and the cfg-message, too.