Do not look for Cargo.toml inside target (rust-lang#15692)

This test, which checks that we do not define new profiles directly in
Clippy's multiple `Cargo.toml` files, must not look inside `target` as
`lintcheck` might place some third-party sources there. Of course those
third-party sources are allowed to define profiles in their
`Cargo.toml`.

changelog: none

Author: Jarcho

tests/no-profile-in-cargo-toml.rs

@@ -17,6 +17,9 @@ fn no_profile_in_cargo_toml() {
     // keep it fast and simple.
     for entry in WalkDir::new(".")
         .into_iter()
+        // Do not recurse into `target` as lintcheck might put some sources (and their
+        //  `Cargo.toml`) there.
+        .filter_entry(|e| e.file_name() != "target")
         .filter_map(Result::ok)
         .filter(|e| e.file_name().to_str() == Some("Cargo.toml"))
     {