Add a mir-opt test for drop shims of arrays

tests/mir-opt/slice_drop_shim.core.ptr-drop_in_place.[String;42].AddMovesForPackedDrops.before.mir

@@ -0,0 +1,55 @@
+// MIR for `std::ptr::drop_in_place` before AddMovesForPackedDrops
+
+fn std::ptr::drop_in_place(_1: *mut [String; 42]) -> () {
+    let mut _0: ();
+    let mut _2: usize;
+    let mut _3: usize;
+    let mut _4: *mut std::string::String;
+    let mut _5: bool;
+    let mut _6: *mut std::string::String;
+    let mut _7: bool;
+
+    bb0: {
+        goto -> bb8;
+    }
+
+    bb1: {
+        return;
+    }
+
+    bb2 (cleanup): {
+        resume;
+    }
+
+    bb3 (cleanup): {
+        _4 = &raw mut (*_1)[_3];
+        _3 = Add(move _3, const 1_usize);
+        drop((*_4)) -> [return: bb4, unwind terminate(cleanup)];
+    }
+
+    bb4 (cleanup): {
+        _5 = Eq(copy _3, copy _2);
+        switchInt(move _5) -> [0: bb3, otherwise: bb2];
+    }
+
+    bb5: {
+        _6 = &raw mut (*_1)[_3];
+        _3 = Add(move _3, const 1_usize);
+        drop((*_6)) -> [return: bb6, unwind: bb4];
+    }
+
+    bb6: {
+        _7 = Eq(copy _3, copy _2);
+        switchInt(move _7) -> [0: bb5, otherwise: bb1];
+    }
+
+    bb7: {
+        _2 = Len((*_1));
+        _3 = const 0_usize;
+        goto -> bb6;
+    }
+
+    bb8: {
+        goto -> bb7;
+    }
+}

tests/mir-opt/slice_drop_shim.rs

@@ -5,6 +5,8 @@
 // if we use -Clink-dead-code.
 
 // EMIT_MIR core.ptr-drop_in_place.[String].AddMovesForPackedDrops.before.mir
+// EMIT_MIR core.ptr-drop_in_place.[String;42].AddMovesForPackedDrops.before.mir
 fn main() {
     let _fn = std::ptr::drop_in_place::<[String]> as unsafe fn(_);
+    let _fn = std::ptr::drop_in_place::<[String; 42]> as unsafe fn(_);
 }