the test suite assumes a libstd with full MIR; run test suite on xargo-built foreign libstds

tests/compile-fail/ptr_offset_overflow.rs

@@ -0,0 +1,6 @@
+//error-pattern: attempt to add with overflow
+fn main() {
+    let v = [1i8, 2];
+    let x = &v[1] as *const i8;
+    let _val = unsafe { x.offset(isize::min_value()) };
+}