Add test for issue-28575

Author: JohnTitor

src/test/ui/intrinsics/issue-28575.rs

@@ -0,0 +1,9 @@
+#![feature(intrinsics)]
+
+extern "C" {
+    pub static FOO: extern "rust-intrinsic" fn();
+}
+
+fn main() {
+    FOO() //~ ERROR: use of extern static is unsafe
+}

src/test/ui/intrinsics/issue-28575.stderr

@@ -0,0 +1,11 @@
+error[E0133]: use of extern static is unsafe and requires unsafe function or block
+  --> $DIR/issue-28575.rs:8:5
+   |
+LL |     FOO()
+   |     ^^^ use of extern static
+   |
+   = note: extern statics are not controlled by the Rust type system: invalid data, aliasing violations or data races will cause undefined behavior
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0133`.