Add ui test for include_file_outside_project lint

tests/ui/include_file_outside_project.rs

@@ -0,0 +1,12 @@
+//@ normalize-stderr-test: "located at `.+/.crates.toml`" -> "located at `$$DIR/.crates.toml`"
+//@ normalize-stderr-test: "folder \(`.+`" -> "folder (`$$CLIPPY_DIR`"
+
+#![deny(clippy::include_file_outside_project)]
+
+// Should not lint.
+include!("./auxiliary/external_consts.rs");
+
+fn main() {
+    let x = include_str!(concat!(env!("CARGO_HOME"), "/.crates.toml"));
+    //~^ include_file_outside_project
+}

tests/ui/include_file_outside_project.stderr

@@ -0,0 +1,15 @@
+error: attempted to include a file outside of the project
+  --> tests/ui/include_file_outside_project.rs:10:13
+   |
+LL |     let x = include_str!(concat!(env!("CARGO_HOME"), "/.crates.toml"));
+   |             ^
+   |
+   = note: file is located at `$DIR/.crates.toml` which is outside of project folder (`$CLIPPY_DIR`)
+note: the lint level is defined here
+  --> tests/ui/include_file_outside_project.rs:4:9
+   |
+LL | #![deny(clippy::include_file_outside_project)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+