perf trace: hello fix libbpf 1.0+ compatibility

Don't use deprecated and now broken map style. Avoid use of
tools/perf/include/bpf/bpf.h and use the more regular BPF headers.

Switch to raw_syscalls:sys_enter to avoid the evlist being empty and
fixing generating output.

Committer testing:

  # perf trace -e ~acme/git/perf/tools/perf/examples/bpf/hello.c --call-graph=dwarf --max-events 5
     0.000 perf/206852 __bpf_stdout__(Hello, world)
                                       syscall_trace_enter.constprop.0 ([kernel.kallsyms])
                                       syscall_trace_enter.constprop.0 ([kernel.kallsyms])
                                       do_syscall_64 ([kernel.kallsyms])
                                       entry_SYSCALL_64_after_hwframe ([kernel.kallsyms])
                                       __GI___sched_setaffinity_new (/usr/lib64/libc.so.6)
     8.561 pipewire/2290 __bpf_stdout__(Hello, world)
                                       syscall_trace_enter.constprop.0 ([kernel.kallsyms])
                                       syscall_trace_enter.constprop.0 ([kernel.kallsyms])
                                       do_syscall_64 ([kernel.kallsyms])
                                       entry_SYSCALL_64_after_hwframe ([kernel.kallsyms])
                                       __libc_read (/usr/lib64/libc.so.6)
     8.571 pipewire/2290 __bpf_stdout__(Hello, world)
                                       syscall_trace_enter.constprop.0 ([kernel.kallsyms])
                                       syscall_trace_enter.constprop.0 ([kernel.kallsyms])
                                       do_syscall_64 ([kernel.kallsyms])
                                       entry_SYSCALL_64_after_hwframe ([kernel.kallsyms])
                                       __GI___ioctl (/usr/lib64/libc.so.6)
     8.586 pipewire/2290 __bpf_stdout__(Hello, world)
                                       syscall_trace_enter.constprop.0 ([kernel.kallsyms])
                                       syscall_trace_enter.constprop.0 ([kernel.kallsyms])
                                       do_syscall_64 ([kernel.kallsyms])
                                       entry_SYSCALL_64_after_hwframe ([kernel.kallsyms])
                                       __GI___write (/usr/lib64/libc.so.6)
     8.592 pipewire/2290 __bpf_stdout__(Hello, world)
                                       syscall_trace_enter.constprop.0 ([kernel.kallsyms])
                                       syscall_trace_enter.constprop.0 ([kernel.kallsyms])
                                       do_syscall_64 ([kernel.kallsyms])
                                       entry_SYSCALL_64_after_hwframe ([kernel.kallsyms])
                                       __timerfd_settime (/usr/lib64/libc.so.6)
  #
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20221103045437.163510-5-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/examples/bpf/hello.c

-#include <stdio.h>
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
 
-int syscall_enter(openat)(void *args)
+struct __bpf_stdout__ {
+	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
+	__type(key, int);
+	__type(value, __u32);
+	__uint(max_entries, __NR_CPUS__);
+} __bpf_stdout__ SEC(".maps");
+
+#define puts(from) \
+	({ const int __len = sizeof(from); \
+	   char __from[sizeof(from)] = from;			\
+	   bpf_perf_event_output(args, &__bpf_stdout__, BPF_F_CURRENT_CPU, \
+			  &__from, __len & (sizeof(from) - 1)); })
+
+struct syscall_enter_args;
+
+SEC("raw_syscalls:sys_enter")
+int sys_enter(struct syscall_enter_args *args)
 {
 	puts("Hello, world\n");
 	return 0;
 }
 
-license(GPL);
+char _license[] SEC("license") = "GPL";