[bazel] Fix build on macOS.

Signed-off-by: Piotr Sikora <piotrsikora@google.com>
Change-Id: I521c3f0c8be13df4b4661a0c1e67d9dd278acbe8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3364916Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78485}

bazel/defs.bzl

@@ -334,6 +334,7 @@ def _v8_target_cpu_transition_impl(settings, attr):
         "haswell": "x64",
         "k8": "x64",
         "x86_64": "x64",
+        "darwin": "x64",
         "darwin_x86_64": "x64",
         "x86": "ia32",
         "ppc": "ppc64",