perf jitdump: Fix a build error with ASAN

perf jitdump: Fix a build error with ASAN

I found this error when I pass EXTRA_CFLAGS=-fsanitize=address on Fedora
44 with GCC 16.  Fix it by copying one less byte.

    CC      util/jitdump.o
  util/jitdump.c: In function ‘jit_process’:
  util/jitdump.c:237:9: error: ‘__builtin_strncpy’ specified bound 4096 equals destination size
                               [-Werror=stringop-truncation]
    237 |         strncpy(jd->dir, name, PATH_MAX);
        |         ^
  cc1: all warnings being treated as errors
  make[4]: *** [tools/build/Makefile.build:95: util/jitdump.o] Error 1
  make[4]: *** Waiting for unfinished jobs....
  make[3]: *** [tools/build/Makefile.build:158: util] Error 2
  make[2]: *** [Makefile.perf:578: perf-util-in.o] Error 2
  make[1]: *** [Makefile.perf:288: sub-make] Error 2
  make: *** [Makefile:76: all] Error 2

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>