Reland "mac: Switch to Xcode 16.0 16A242d with macOS SDK 15.0 24A336"

This is a reland of fbc74102ad59
(https://chromium-review.googlesource.com/c/5868532), which was reverted
in 1bf416f7ddf0 (https://chromium-review.googlesource.com/c/5867385)
because it caused Mac ASan 64 Builder to fail its compile step in the
generate_v8_context_snapshot step (https://crbug.com/367764848).

This can reland atop daa2e0a59313
(https://chromium-review.googlesource.com/c/5873781), which should
prevent generate_v8_context_snapshot from failing under Address
Sanitizer.

Original change's description:
> mac: Switch to Xcode 16.0 16A242d with macOS SDK 15.0 24A336
>
> FOR CHECKIN
> FOR CHICKEN
> PARA POLLO
> POUR LE POULET
> 🐣
>
> Bug: 367439535
> Change-Id: I13c4849eddb458b76d973dcc059c7043b63b4245
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5868532
> Reviewed-by: Nico Weber <thakis@chromium.org>
> Commit-Queue: Mark Mentovai <mark@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1356474}

Bug: 367439535
Change-Id: I63b4a8072ba453291c22da5f6b37b16a6a4190c3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5873345
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Auto-Submit: Mark Mentovai <mark@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1357347}