Fix assignment to non-lvalue storage values.

test/libsolidity/semanticTests/array/copying/array_copy_including_array.sol

@@ -33,6 +33,8 @@ contract c {
         return (small.length, large.length);
     }
 }
+// ====
+// compileViaYul: also
 // ----
 // test() -> 0x02000202
 // storage: empty

test/libsolidity/semanticTests/array/pop/array_pop_array_transition.sol

@@ -21,6 +21,8 @@ contract c {
         delete inner;
     }
 }
+// ====
+// compileViaYul: also
 // ----
 // test() -> 1, 2, 3
 // storage: empty