perf tests: Avoid raising SEGV using an obvious NULL dereference

An optimized build such as:

  make -C tools/perf CLANG=1 CC=clang EXTRA_CFLAGS="-O3

will turn the dereference operation into a ud2 instruction, raising a
SIGILL rather than a SIGSEGV. Use raise(..) for correctness and clarity.

Similar issues were addressed in Numfor Mbiziwo-Tiapo's patch:

  https://lkml.org/lkml/2019/7/8/1234

Committer testing:

Before:

  [root@quaco ~]# perf test hooks
  55: perf hooks                                            : Ok
  [root@quaco ~]# perf test -v hooks
  55: perf hooks                                            :
  --- start ---
  test child forked, pid 17092
  SIGSEGV is observed as expected, try to recover.
  Fatal error (SEGFAULT) in perf hook 'test'
  test child finished with 0
  ---- end ----
  perf hooks: Ok
  [root@quaco ~]#

After:

  [root@quaco ~]# perf test hooks
  55: perf hooks                                            : Ok
  [root@quaco ~]# perf test -v hooks
  55: perf hooks                                            :
  --- start ---
  test child forked, pid 17909
  SIGSEGV is observed as expected, try to recover.
  Fatal error (SEGFAULT) in perf hook 'test'
  test child finished with 0
  ---- end ----
  perf hooks: Ok
  [root@quaco ~]#

Fixes: a074865e60ed ("perf tools: Introduce perf hooks")
Signed-off-by: Ian Rogers <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Wang Nan <[email protected]>
Link: http://lore.kernel.org/lkml/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

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