when -Zrandomize-layout is enabled disable alloc test testing internal struct sizes

Author: the8472

library/alloc/Cargo.toml

@@ -52,4 +52,5 @@ check-cfg = [
     'cfg(no_global_oom_handling)',
     'cfg(no_rc)',
     'cfg(no_sync)',
+    'cfg(randomized_layouts)',
 ]

library/alloc/src/collections/btree/node/tests.rs

@@ -90,7 +90,7 @@ fn test_partial_eq() {
 
 #[test]
 #[cfg(target_arch = "x86_64")]
-#[cfg_attr(miri, ignore)] // We'd like to run Miri with layout randomization
+#[cfg_attr(any(miri, randomized_layouts), 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);

src/bootstrap/src/core/builder.rs

@@ -2193,6 +2193,9 @@ impl<'a> Builder<'a> {
                 rustflags.arg("-Zvalidate-mir");
                 rustflags.arg(&format!("-Zmir-opt-level={mir_opt_level}"));
             }
+            if self.config.rust_randomize_layout {
+                rustflags.arg("--cfg=randomized_layouts");
+            }
             // Always enable inlining MIR when building the standard library.
             // Without this flag, MIR inlining is disabled when incremental compilation is enabled.
             // That causes some mir-opt tests which inline functions from the standard library to