Update check-cfg lists for alloc

Author: tesuji

library/alloc/Cargo.toml

@@ -40,3 +40,12 @@ compiler-builtins-weak-intrinsics = ["compiler_builtins/weak-intrinsics"]
 panic_immediate_abort = ["core/panic_immediate_abort"]
 # Choose algorithms that are optimized for binary size instead of runtime performance
 optimize_for_size = ["core/optimize_for_size"]
+
+[lints.rust.unexpected_cfgs]
+level = "warn"
+check-cfg = [
+    'cfg(no_global_oom_handling)',
+    'cfg(bootstrap)',
+    'cfg(no_rc)',
+    'cfg(no_sync)',
+]