perf build: Don't use -ffat-lto-objects in the python feature test when building with clang-13

Using -ffat-lto-objects in the python feature test when building with
clang-13 results in:

  clang-13: error: optimization flag '-ffat-lto-objects' is not supported [-Werror,-Wignored-optimization-argument]
  error: command '/usr/sbin/clang' failed with exit code 1
  cp: cannot stat '/tmp/build/perf/python_ext_build/lib/perf*.so': No such file or directory
  make[2]: *** [Makefile.perf:639: /tmp/build/perf/python/perf.so] Error 1

Noticed when building on a docker.io/library/archlinux:base container.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Fangrui Song <maskray@google.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Keeping <john@metanate.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>