linux-user/elfload: Fix pr_pid values in core files

linux-user/elfload: Fix pr_pid values in core files

Analyzing qemu-produced core dumps of multi-threaded apps runs into:

    (gdb) info threads
      [...]
      21   Thread 0x3ff83cc0740 (LWP 9295) warning: Couldn't find general-purpose registers in core file.
    <unavailable> in ?? ()

The reason is that all pr_pid values are the same, because the same
TaskState is used for all CPUs when generating NT_PRSTATUS notes.

Fix by using TaskStates associated with individual CPUs.

Cc: qemu-stable@nongnu.org
Fixes: 243c47066253 ("linux-user/elfload: Write corefile elf header in one block")
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20240801202340.21845-1-iii@linux.ibm.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>