Linker error when using Rust 1.89.0 targeting iOS

[UebelAndre]

Observed when implementing #3562

(18:52:04) ERROR: /Users/buildkite/builds/bk-macos-arm64-zv1e/bazel/rules-rust-rustlang/examples/ios/BUILD.bazel:36:18: Linking macos_app_bin failed: (Exit 1): wrapped_clang failed: error executing ObjcLink command (from target //:macos_app)
  (cd /private/var/tmp/_bazel_buildkite/06c9f8f0144a76b4a8f151dd1b9a8bad/sandbox/darwin-sandbox/24/execroot/_main && \
  exec env - \
    APPLE_SDK_PLATFORM=MacOSX \
    APPLE_SDK_VERSION_OVERRIDE=15.2 \
    PATH=/Users/buildkite/Library/Caches/bazelisk/downloads/sha256/0cac3a67dc5429c68272dc6944104952e9e4cf84b29d126a5ff3fbaa59045217/bin:/opt/homebrew/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/bin:/bin:/usr/sbin:/sbin:/opt/homebrew/bin \
    RELATIVE_AST_PATH=true \
    XCODE_VERSION_OVERRIDE=16.2.0.16C5032a \
  bazel-out/darwin_arm64-opt-exec-ST-d57f47055a04/bin/external/apple_support+/crosstool/wrapped_clang @bazel-out/darwin_arm64-fastbuild-macos-arm64-min10.15-applebin_macos-ST-7220d592c911/bin/macos_app_bin-0.params)
# Configuration: 69b35f7f26bce24cbaef608856d16fc8b27171e4c30285bcf99d6bc8dfccc73d
# Execution platform: @@platforms//host:host
Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
Undefined symbols for architecture arm64:
  "__RNvCs73fAdSrgOJL_7___rustc12___rust_alloc", referenced from:
      core::ops::function::FnOnce::call_once$u7b$$u7b$vtable.shim$u7d$$u7d$::h83b25446a3710b5a in libstd-c34d9c6bd90bce09.a[3](std-c34d9c6bd90bce09.std.cb77c4d3935a8f9e-cgu.0.rcgu.o)
      core::ops::function::FnOnce::call_once$u7b$$u7b$vtable.shim$u7d$$u7d$::hda98b980b7e364a0 in libstd-c34d9c6bd90bce09.a[3](std-c34d9c6bd90bce09.std.cb77c4d3935a8f9e-cgu.0.rcgu.o)
      core::cell::once::OnceCell$LT$T$GT$::try_init::hec4c6057203f18ca in libstd-c34d9c6bd90bce09.a[3](std-c34d9c6bd90bce09.std.cb77c4d3935a8f9e-cgu.0.rcgu.o)
      core::cell::once::OnceCell$LT$T$GT$::try_init::hec4c6057203f18ca in libstd-c34d9c6bd90bce09.a[3](std-c34d9c6bd90bce09.std.cb77c4d3935a8f9e-cgu.0.rcgu.o)
      core::cell::once::OnceCell$LT$T$GT$::try_init::hec4c6057203f18ca in libstd-c34d9c6bd90bce09.a[3](std-c34d9c6bd90bce09.std.cb77c4d3935a8f9e-cgu.0.rcgu.o)
      core::cell::once::OnceCell$LT$T$GT$::try_init::hec4c6057203f18ca in libstd-c34d9c6bd90bce09.a[3](std-c34d9c6bd90bce09.std.cb77c4d3935a8f9e-cgu.0.rcgu.o)
      core::slice::sort::stable::driftsort_main::h521ab17a5a757164 in libstd-c34d9c6bd90bce09.a[3](std-c34d9c6bd90bce09.std.cb77c4d3935a8f9e-cgu.0.rcgu.o)
      ...
  "__RNvCs73fAdSrgOJL_7___rustc14___rust_dealloc", referenced from:
      core::ops::function::FnOnce::call_once$u7b$$u7b$vtable.shim$u7d$$u7d$::h9b4a9096c70fd176 in libstd-c34d9c6bd90bce09.a[3](std-c34d9c6bd90bce09.std.cb77c4d3935a8f9e-cgu.0.rcgu.o)
      core::ops::function::FnOnce::call_once$u7b$$u7b$vtable.shim$u7d$$u7d$::hf6b8b73c99aa7295 in libstd-c34d9c6bd90bce09.a[3](std-c34d9c6bd90bce09.std.cb77c4d3935a8f9e-cgu.0.rcgu.o)
      core::ptr::drop_in_place$LT$alloc..vec..Vec$LT$$LP$std..ffi..os_str..OsString$C$std..ffi..os_str..OsString$RP$$GT$$GT$::h54613c9c01320632 in libstd-c34d9c6bd90bce09.a[3](std-c34d9c6bd90bce09.std.cb77c4d3935a8f9e-cgu.0.rcgu.o)

https://buildkite.com/bazel/rules-rust-rustlang/builds/15278/steps/canvas?sid=0198d2b0-5a21-43f4-9690-9494eddda240

[krasimirgg]

Looks like #3459. There's a new opt-in --//rust/settings:experimental_use_allocator_libraries_with_mangled_symbols to switch to allocator mangling written in rust; that depends on unstable features and only works if using a nightly channel of the rust toolchain (not sure what channel the macos build bots are using).