aosp: report POSIX symlink st_size from lstat

[rogerzanoni]

POSIX requires a symlink's st_size to be the length of its target path. Android's /data filesystem reports a different value.

Fixes the following issues in tests
posix_lstat_test.cc:97 EXPECT_EQ(sb.st_size, target_filename.length())

Bug: 532068409

[github-actions]

🤖 Gemini Suggested Commit Message

---

starboard: Fix symlink st_size in fstatat

POSIX requires a symbolic link's st_size to be the length of its target
path. However, Android's /data filesystem may report a different value,
leading to inconsistencies and test failures.

The Starboard POSIX wrapper for fstatat now ensures the reported size
matches the target path length when querying symbolic links without
following them.

Bug: 532068409

---

💡 Pro Tips for a Better Commit Message:

1. Influence the Result: Want to change the output? You can write custom prompts or instructions directly in the Pull Request description. The model uses that text to generate the message.
2. Re-run the Generator: Post a comment with: /generate-commit-message

[gemini-code-assist]

Code Review

This pull request updates __abi_wrap_fstatat to normalize symlink sizes on platforms like Android by querying the target path length via readlinkat. The reviewer pointed out that readlinkat could fail and pollute errno even when the wrapper returns success, and suggested saving and restoring errno around the call to prevent this side effect.

[andrewsavage1]

We should only change the posix wrappers to have it conform with posix specifications, not use it to support platform-specific quirks. Unless it's not possible, this change should be implemented as an android-specific wrapper, similar to the asset management with stat/open

[rogerzanoni]

@andrewsavage1 moved the fix to the posix_emu wrapper

[andrewsavage1]

@rogerzanoni you need to fix the lint checks here