RFR: 8365296: Build failure with Clang due to -Wformat warning after JDK-8364611

[Guanqiang Han]

This issue is related to the definition of __sigset_t (__sigset_t  act.sa_mask).   In the glibc source, __sigset_t is defined in multiple places:  
- bits/types/__sigset_t.h 
<img width="1071" height="415" alt="image02" src="https://github.com/user-attachments/assets/4dff7546-f0b3-448c-832f-54f7b9ffc476" />


- sysdeps/unix/sysv/linux/bits/types/__sigset_t.h (introduced after glibc 2.25)   
<img width="1059" height="487" alt="image01" src="https://github.com/user-attachments/assets/54101f9b-3b1a-4943-83ee-6f6471c060a6" />


During compilation with Clang, the latter definition appears to be used, where __sigset_t is a struct, causing the printf("%X", act.sa_mask) to fail.

we can detect whether _SIGSET_NWORDS is defined and handle the printing differently based on that, ensuring correct handling of the struct type.

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Commit messages:
 - 8365296: Build failure with Clang due to -Wformat warning after JDK-8364611

Changes: https://git.openjdk.org/jdk/pull/26771/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26771&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365296
  Stats: 10 lines in 1 file changed: 8 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/26771.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26771/head:pull/26771

PR: https://git.openjdk.org/jdk/pull/26771