Failure to build Bazel 8.7.0

### Description of the bug:

cc @giordano @mofeing

```
[15:59:24] DEBUG: /workspace/srcdir/.tmp/bazel_XXjBpPjj/out/external/protobuf+/protobuf.bzl:650:10: The py_proto_library macro is deprecated and will be removed in the 30.x release. switch to the rule defined by rules_python or the one in bazel/py_proto_library.bzl.
--
  | 2026-06-29 17:59:28 CEST | [15:59:25] INFO: Analyzed target //src:bazel_nojdk (461 packages loaded, 12969 targets configured).
  | 2026-06-29 17:59:28 CEST | [15:59:28] ERROR: /workspace/srcdir/src/BUILD:79:10: Symlinking //src:zip_builtins [for tool] failed: failed to create symbolic link 'bazel-out/k8-opt-exec-ST-fad1763555eb/bin/src/zip_builtins': file 'src/zip_builtins.sh' is not executable
```

Full log is attached.

[yggdrasil_build_30614_build-b-slash-bazel-x86-64-linux-musl-cxx11.log](https://github.com/user-attachments/files/29472912/yggdrasil_build_30614_build-b-slash-bazel-x86-64-linux-musl-cxx11.log)

### Which category does this issue belong to?

Core

### What's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

_No response_

### Which operating system are you running Bazel on?

_No response_

### What is the output of `bazel info release`?

_No response_

### If `bazel info release` returns `development version` or `(@non-git)`, tell us how you built Bazel.

_No response_

### What's the output of `git remote get-url origin; git rev-parse HEAD` ?

```text

```

### If this is a regression, please try to identify the Bazel commit where the bug was introduced with bazelisk --bisect.

_No response_

### Have you found anything relevant by searching the web?

_No response_

### Any other information, logs, or outputs that you want to share?

_No response_

Start with the attached build log and inspect src/BUILD around line 79 together with src/zip_builtins.sh. Reproduce the Bazel 8.7.0 build in the reported environment, then verify that the //src:zip_builtins symlink is created successfully without the non-executable-file error.

Written by the indexing model from the issue text.