perf python: Allow checking for the existence of warning options in clang

perf python: Allow checking for the existence of warning options in clang

We'll need to check if an warning option introduced in clang 19 is
available on the clang version being used, so cover the error message
emitted when testing for a -W option.

Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/lkml/CA+icZUVtHn8X1Tb_Y__c-WswsO0K8U9uy3r2MzKXwTA5THtL7w@mail.gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>