lib_pathbuffer: change nxmutex -> spinlock

[crafcat7]

Summary:

Summary

Change nxmutex to spinlock to fix bug:

_assert
|
 ->dump_fatal_info
   |
    ->dump_tasks
      |
       ->dump_filelist
         |
          ->files_dumplist
            |
             ->lib_get_pathbuffer
               |
                ->nxmutex_lock      <-- hold mutex on assert will trigger an nested exception

Impact

Is a new feature added?: NO
Impact on build: NO
Impact on hardware: NO, this change does not specifically target any particular hardware architectures or boards.
Impact on documentation: NO,This patch does not introduce any new features
Impact on compatibility: This implementation aims to be backward compatible. No existing functionality is expected to be broken.

Testing

Build Host(s): Linux x86
Test cases based on local qemu environment passed

[nuttxpr]

[Experimental Bot, please feedback here]

Yes, this PR mostly meets the NuttX requirements, but could be improved.

Here's what's good:

• Clear problem description: The summary clearly identifies the bug and its root cause with a helpful stack trace.
• Impact assessment: Addresses all impact points.
• Testing information: Provides host and target information, and mentions passing tests.

Here's what needs improvement:

• Summary - "How does the change exactly work?" is missing: While the "why" is clear, the PR description lacks detail on how nxmutex is changed to a spinlock. Explain the specific code changes made. For example: "This PR replaces the nxmutex_lock call in lib_get_pathbuffer with a spinlock. A new spinlock variable, g_pathbuffer_lock, is declared statically in the file and initialized during system startup." Be precise.
• Missing "Testing logs before/after change": While it mentions tests passing, it needs to show actual log output demonstrating the fix. Include relevant snippets demonstrating the error before the change and its absence after. Empty code blocks are insufficient.
• Target details lacking: "local qemu environment" is vague. Specify the QEMU architecture being used (e.g., qemu-arm, qemu-riscv). Mention the specific NuttX configuration (e.g., nsh).

By adding these details, the PR will be much stronger and easier to review.

[hujun260]

->nxmutex_lock <-- hold mutex on assert will trigger an nested exception

Is this exception caused because assert is called within an interrupt?

[xiaoxiang781216]

->nxmutex_lock <-- hold mutex on assert will trigger an nested exception

Is this exception caused because assert is called within an interrupt?

lib_get_pathbuffer is used in many places, so it's better to the interrupt safe.

[hujun260]

LGTM