test referencing unsupported extern static

tests/compile-fail/extern_static.rs

@@ -0,0 +1,10 @@
+#![feature(raw_ref_op)]
+//! Even referencing an unknown `extern static` already triggers an error.
+
+extern "C" {
+    static mut FOO: i32;
+}
+
+fn main() {
+    let _val = unsafe { &raw const FOO }; //~ ERROR is not supported by Miri
+}