Auto merge of #9074 - daxpedda:equatable-if-let-external-macro, r=Manishearth

Fix false-positive in `equatable_if_let`

Was linting in external macros. I guess now that I know about https://github.com/rust-lang/rust-clippy/pull/8694 it seems all kinda pointless until we resolve that.

Nevertheless, it's an improvement.

Fixes #9066.

changelog:`equatable_if_let` No longer lint on macros