Add PTRACE_GET_SYSCALL_INFO

[maxbla]

target triple: unknown-linux-*
docs: https://man7.org/linux/man-pages/man2/ptrace.2.html

PTRACE_GET_SYSCALL_INFO is a linux-specific api (added fairly recently in Linux 5.3) that gives the consumer information about ptrace syscall stops, like if it was syscall entry or exit. Adding support would require a rust definition for the main data structure -

struct ptrace_syscall_info {
    __u8 op;         /* Type of system call stop */
    __u32 arch;      /* AUDIT_ARCH_* value; see seccomp(2) */
    __u64 instruction_pointer; /* CPU instruction pointer */
    __u64 stack_pointer;       /* CPU stack pointer */
    union {
        struct {     /* op == PTRACE_SYSCALL_INFO_ENTRY */
            __u64 nr;          /* System call number */
            __u64 args[6];     /* System call arguments */
        } entry;
        struct {     /* op == PTRACE_SYSCALL_INFO_EXIT */
            __s64 rval;        /* System call return value */
            __u8 is_error;     /* System call error flag;
                                  Boolean: does rval contain
                                  an error value (-ERRCODE) or
                                  a nonerror return value? */
        } exit;
        struct {     /* op == PTRACE_SYSCALL_INFO_SECCOMP */
            __u64 nr;          /* System call number */
            __u64 args[6];     /* System call arguments */
            __u32 ret_data;    /* SECCOMP_RET_DATA portion
                                  of SECCOMP_RET_TRACE
                                  return value */
        } seccomp;
    };
};

in addition to adding the PTRACE_GET_SYSCALL_INFO constant

I could submit a PR for this if it might be merged.