Add NT_SIGINFO NOTE for each thread to createdump dumps

[mikem8361]

On Linux, add the NT_SIGINFO note for each thread. This NOTE contains the siginfo_t struct which can be obtained with ptrace's PTRACE_GETSIGINFO or PTRACE_PEEKSIGINFO (doesn't remove signals).

See https://man7.org/linux/man-pages/man2/ptrace.2.html on ptrace.

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[mikem8361]

This helps native debuggers like lldb/gdb and windbg to get more info on native exceptions/signals.

[hoyosjs]

Is this SA_SIGINFO? Actually looks this is different.

[mikem8361]

SA_SIGINFO is the sigaction() flag used when setting an signal handler. The siginfo_t struct is passed to the handler if SA_SIGINFO is passed to sigaction.

NT_SIGINFO is a NOTE in the ELF coredump containing the signal info. This note contains a siginfo_t struct for the thread.