add patch to disable layout-dependent test

Author: RalfJung

rust-src.diff

@@ -0,0 +1,12 @@
+diff --git a/library/alloc/src/collections/btree/node/tests.rs b/library/alloc/src/collections/btree/node/tests.rs
+index aadb0dc9c40..64bce0ff8c0 100644
+--- a/library/alloc/src/collections/btree/node/tests.rs
++++ b/library/alloc/src/collections/btree/node/tests.rs
+@@ -94,6 +94,7 @@ fn test_partial_eq() {
+ 
+ #[test]
+ #[cfg(target_arch = "x86_64")]
++#[cfg_attr(miri, ignore)] // We'd like to run Miri with layout randomization
+ fn test_sizes() {
+     assert_eq!(core::mem::size_of::<LeafNode<(), ()>>(), 16);
+     assert_eq!(core::mem::size_of::<LeafNode<i64, i64>>(), 16 + CAPACITY * 2 * 8);